It is far too complex to be explained fully here. All files by that name will be printed. See the manpage for more details. There is also a command, 'where', that will search your PATH string for a command. You can use this command, such as where chmod to find the location of the program chmod.
Files ending in .c are C programs.
They can be compiled using either cc or gcc. All you have to do is type make and it will compile the files for you. It's as simple as ls . Use chmod . For files, rm file .