I think you are in for a lot of reading, and a lot of fun.
The earlier comments apply, I have no argument with anything said so far.
I do want to add one thing: $PATH is an environment variable, not a function or utility. The difference may be critical.
It does not accumulate: ie a second assignment REPLACES the first.
For example the following sequence
would generate output something like
There are some script and program utilities that allow you to pass a parameter, and (assuming it is a folder) they will check the current PATH and optionally add or remove it from the path as needed. (Testing to ensure that no path is added twice, etc.)
I know of no one who uses them extensively for anything other than startup scripts and automation. (pathmung come to mind)
An effect something LIKE those functions is easy to provide using a technique like this:
might result in output that looks like
I hope this helps.