I’m not the best person to explain this, but I’ll give it a shot…
Many people who want to learn programming or are beginners ask questions like “which language should I use?”, “what is the BEST framework?” or “what are the most important algorithms / control structures / patterns I should learn?” And the answer to all those questions is that, it doesn’t matter. You can start with anything and later learn new things as you go on. There are some languages that are easier to work with, which I recommend starting out with in order to keep up your interest and keep programming.
The most important thing is to get started. Just start with the first tutorial on https://www.codecademy.com/ or pick some other programming learning resource, and stick with it. Once you have learned to think like a programmer it is very easy to pick up most new languages.
And to answer your literal question more directly, I’ll just say that everything is an algorithm and there isn’t any magical one that is more important the others. Once you have programming skills you should be able to by just reading the thrive code understand the general gist of what is going on.
This is also good advice. Once you know the programming basics you should start a simple project you can finish and gain experience with. It might be a bit rough to try to understand enough of the Thrive code to make changes if you have not worked on any software projects before.
Edit: I personally like https://www.freecodecamp.org/ more than codecademy as that is completely free and open source. I just grabbed the first link from our learning skills wiki page and didn’t notice it wasn’t what I meant to link.