Explaining like you are 5:
If you have worked with programming languages, you might have come across global variables and inbuilt functions/keywords. PATH is a similar global variable for your terminal session.
Every time you open up a terminal, you load up these "global variables", and you/programs can access them (or the applications assigned to them).
So, let's say you have your application (executable) as /home/werecat/corncob/bin/corn, instead of starting it with ./home/werecat/corncob/bin/corn ..., if you have /home/werecat/corncob/bin in your PATH variable, you can just use it as corn ....
export PATH="/home/werecat/corncob/bin:$PATH"
just means:
PATH = /home/werecat/corncob/bin + PATH- persist (export) path for the duration of this session (usually until you close the terminal tab)
If you see somewhere to add it to your /home/werecat/.bashrc file, it means "all commands in .bashrc file are auto-executed every time you start a new terminal session, so if you have it there, you won't need to manually keep entering the command over and over again".
You can list these environment variables by just running:
env
Also, recommend you have a look at https://www.freecodecamp.org/news/how-to-set-an-environment-variable-in-linux/.
Hope this helps. Good luck on your Linux journey.
Don't think he has the time though.