How to use the man pages. Conventions used in this Document and General Reference. It is an amazing set of projects, all written from scratch and placed in the public domain for all of us. The first thing to remember is that most UNIX commands are just shorthand versions of what you'd say in English, anyway.
Most commands have flag options.
Sometimes this is ok, most often this is very bad, as you recursively descend in your directory structure deleting all files, instead of the files in a subdirectory as you had intended. This invokes the on-line manual. Man will inform you of the proper syntax, use, and flags which can be used with a command. UNIX is a very powerful and flexible system, with capabilities far beyond what most of us from our desktop system. It is a wonderful and powerful tool, by it's very nature, the line between program, operating system and languages blurs, to the user's ultimate benefit.