A few links that might help with PATH variable understanding and management:
A message I wrote to a student in attempt to explain PATH:
"PATH is a list of folders (or directories, same thing). It comes into play when using the command line. In a normal, hierarchical filesystem (where you can have folders inside of folders) there can be many, many folders and if there's a program in one of them somewhere, when you call it from the command line it is necessary to locate it. Maybe you give the exact, full name of it including the folder(s) within which it lies. So if you have directories named /a, /b/, /c and also /alpha, /beta, /gamma and your program inhabits /beta then it will be findable and executed if you call it by writing " /beta/myprogram " on the command line. But we don't usually do that. Instead we just write an abbreviated " myprogram ". That leaves it ambiguous. Is it /c/myprogram? Could it be /gamma/myprogram? In the real world there might not be 6 folders in the filesystem, but 600 or 6000. You can't just guess. So the solution is to have a small number of select, designated folders in which you put all your programs, then make a list of them. The system searches for "myprogram" successively in each folder in that list. As long as myprogram was placed in one of the designated folders it'll get found. Problem solved. Where is the list? It's kept in a variable, named PATH."