This article explains the difference between themes and templates in Blogger, Google's blogging tool.
What is (was) a Blogger template
How a blog that is made with Blogger is shown to a visitor is controlled by four sets of information:
The posts which the blogger writes (ie the content)
A user-editable "configuration file" which records the overall formatting options which the file designer and then the blogger have chosen
Another configuration file, called the post-template, which records choices that the blogger has made under Layout > Blog posts (edit), but cannot be edited elsewhere.
Blogger's own software, which puts the other things together with some internal rules to make "web pages". Bloggers cannot control the rules in this at all.
Originally, the first "configuration file" was called a template. In fact, officially it was called a design-template, to distinguish it from the post-template. However because most people aren't aware of the post template, usually just the word "template" is used to mean design-template.
What is a theme
Other blogging tools (eg Wordpress, Tumblr) called their equivalent file a theme. Most (or even all) of those tools provide less access to change things in the Theme file, for example if you use a Wordpress free-hosted blog, then you cannot change any of the code in your theme, you can only make formatting changes which are allowed for in the Wordpress front-end.
Many of the Wordpress themes have had a lot of graphic design work done on them - using them gives a blog-site which looks very attractive (or otherwise suited for their purpose) on a wide range of screens. Many large websites have been made using Wordpress, and so very many professional designers have created Wordpress themes. Because of this, many people believe that it's easier to get an excellent-looking website from a theme than from a Blogger template.
Blogger templates have now become themes
Recently - I noticed it in March 2017 - Blogger started calling their templates "themes".
They've changed the menu option on their dashboard from "Template" to "Theme".
They've changed the action button names in the template/theme editor to say things like "Save theme".
They've written various help articles which refer to themes.
What hasn't changed
We can still edit our templates themes extensively.
The Blogger tools that make the changes in our themes haven't changed: All the items under the Themes tab on the dashboard are the same as the ones on the Templates tab.
The contents of our existing themes are still much the same (I cannot guarantees they haven't made any changes, but I haven't seen any)
The themes that we can choose from when making a new blog, or changing the format of an existing one, are the same.
There are hundreds of help and how-to articles written by blogger-helpers like myself, which all refer to templates. (I've started changing mine - but it's going to take a while!)
What else is going to change?
This is the big question: Is the rename a precursor to some other changes, eg restricting how much control we have over our themes? - or is it just a cosmetic change to make Blogger seem more modern?
Will there be some new themes released - ones that look better across a range of devices, maybe even some that are optimized for mobile instead of desktop use?
Will there be new theme-editing features introduced into Blogger's interface, to let us control things we cannot control now?
Conclusion / TL-DR
Only Google's Blogger product managers know exactly what the future plans for Blogger are - and they're not known for talking about the future direction until they're just about to introduce new features.
But until they do, my conclusion is that there is no difference between templates and themes in Blogger. They are simply two different words for exactly the same thing.
NB: Blogger product a announcements are usually made in the Blogger Buzz blog - and I see that template were still called templates in their most recent post in November 2016:
Proud to have worked on National Geographic's new series, Origins : The Journey of Humankind. Premieres tonight in the US at 9 pm ET. I worked on eight languages for it!
Lydian
Gaulish
Proto-Indo-European
Germanic-flavored Proto-Indo-European
Nostratic
Proto-Afro-Asiatic
Basque-flavored Proto-Dene-Caucasian\\
Proto Pama-Nyungan
Hopefully (if I get approval from the powers that be), I'll be able to go into some detail here about my work on the show.
Today we'll look at Wuga's scenes (known as Wogah in the game), a quirky, one-armed crafter who introduces Takkar to Wugas fnagu "Woga's claw" and a whole host of upgrades.
Played by the extremely talented (and extremely kind) Ron Kennell, I smile every time I hear him yell "Fmaygan". Mi-sharm hadarsh!
Nay! Mu supima Winja! Ta dijam-shanti, fmayga-su tagata. Udam-war-way. No! I last Wenja! You dirt-face, piss-in covered. Udam-just-like. No! I'm the last Wenja! You're a dirt face, covered in piss. Just like Udam. Smarka, Fmaygan. Bye, Pisser/Pissee. Bye, Piss-man. (Fun fact : the suffix -an can mark an agent noun, equivalent to the -er suffix in English. So, shaja "lead" + -an = shajan "leader". BUT it also marks the recipient of an action, so technically shajan can mean "leadee; the one who is lead". This is much less common in Wenja. But this is precisely what the -an in Fmaygan is doing. Wuga is really drawing attention to the fact that he peed on Takkar)
Palhu gwayfarsh, na mayta ti-way. Many live-they, not crazy you-like Many live, not crazy like you.
Wuga:
Nam mayta. Winja sakwim! Not-I crazy. Wenja help-I! I'm not crazy. I help Wenja!
Pashta? Kala. Saywa shash-way. Hasar Urusis. See-you? Pretty. Hard rock-like. Blood Oros-of. You see? Pretty. Hard as a rock. Blood of Oros.
Bal Winja tachisla dahay su. Ma Hasar Urusis mibi chawda. Strong Wenja weapons make-for good. But Blood Oros-of me-from hides. Good for making strong Wenja weapons. But Blood of Oros hides from me.
Takkar :
Shash waydam. U nartar hay - u Winja-ha gwayfa. Rocks find-I. COMMAND west go - COMMAND Wenja-with live. I find the stones. You go west - live with Wenja.
Wuga:
Buda Fmaygan. Sashwalsu dayshan Hasar Urusis sansha. Hay miyi. Smart Pissee. Sun-in shining Blood Oros-of Seek. This me-for. Smart Piss-man. Look for the Blood of Oros shining in the sun. This one's mine. (You can see that -an also is equivalent to -ing in English : daysha "to shine" : dayshan "shining". Very useful suffix)
Peak of Oros
Wuga:
Fmaygan! Mu bal damshi tatishta. Nu-ta bal fnagu taticham! Pissee! Me strong hut build-you. Now-you strong claw build-I!
Piss-man! You built me a strong hut. Now I build a strong claw for you!
Kwayda shanchim, u apa gwam. Tu kwarkwar shwaldata darfata-kwa! When stop-I, COMMAND back come. Then wherewhere climb-you jump-you-and!
When I finish, you come back. Then you climb and jump anywhere!
(If you haven't noticed already, the basic word for "and" is -kwa and it comes after the 2nd thing it's conjoining. So: Winja Izila-kwa = "Wenja & Izila". Nu can also mean "and", though it only occurs at the beginning of a sentence: Nu shawsi Ulls hinacha "And take Ull's ear!")
Takkar :
Hay-ha shwaldam darfam-kwa. This-with climb-I jump-I-and. I climb and jump with this.
Wuga:
Wugas fnagu! Waydata! Woga-of claw! Found-it!
Woga's claw! You found it!
Su fnagu! U barju yaha, shwalda. Good claw! COMMAND high throw, climb.
A good claw. Throw high, climb up.
Faran parkun! U-ra fnagu bawga, ha farun parkun shwalda. Su ha nawa kwarwi taticha. Eagle feather! COMMAND-REFLEXIVE claw be.useful, so.that eagle feather climb. Good so.that new tool make.
Eagle feather! Use claw to climb eagle cliff. Good to make new tools.
Na kwarwi bal Wugas fnagu-way! Not tool strong Woga-of claw-like!
Udam beasts attack old Wenja home, break totem - eat my arm!
Na sharm yakam, ma chwanta yakam! Not arm fix-I, but totem fix-I!
I didn't fix my arm, but I did fix the totem.
Udam gwan, Fmaygan. Chwanta sakman hinacha. Tu nawa Winja chwanta damsham! Udam kill, Pissee. Totem scraps take. Then new Wenja totem build-I! Kill Udam, Piss Man. Take back totem scraps. Then I build new Wenja totem.
Wuga:
Apa, apa! Kuswa dashta! Back, Back! Almost done!
Back, back! Almost done!
Kakura, piki, Udam hasar!
Dung, tar, Udam blood! Dung, tar, Udam blood!
Chwanta saywa daha, darwa-way. Totem hard make, tree-as.
Makes totem hard as tree.
Dashta! Done!
Done!
Takkar :
Bal. Winja shayu-way. Strong. Wenja spirit-like Strong. Like Wenja spirit.