What am I looking at?
You are looking at an implementation of dodge-the-creeps with godot and gdext. It is a tutorial that compiles and runs. However there are steps which must be done in the godot editor. Those steps you will be pointed at the official gdscript dodge the creeps tutorial.
This tutorial is done in a literate style which means you’ll see some weird symbols that aren’t legal rust. These are placeholders stating “put a code block here.” It is somewhat helpful from a learning standpoint as it forces a high level overview to help comprehension. The patterns of files will become aparent to you far before the conventions of gdext. It also means, as stated earlier, that these text files you read right now can be compiled into an executable and run. If it is in this tutorial it will run. You can see more about this at the github for this tutorial
TLDR: If you see <<some words in double angle braces>> this means a code block goes there. Don’t put it in your rust file.