As usual, if you don’t know what Adaptive Cards are you probably want to read a bit about them first. The easiest start is by just going to www.adaptivecards.io, play a bit with the designer there, have a look at the samples and get a feeling what all this is about. Just come back here
Working with API's is all about JSON these days. Like all these SAAS products, big platforms like Microsoft or Google, all speak Rest and JSON. However, when working with API's you can find a lot of code in C# or GO or PHP or whatever else that is really odd when you think of it.