The where, whereis and whatis commands summarize commands, show where executables are, and point to relevant man pages.

You need to understand the Linux directory structure, get comfortable using the terminal, familiarize yourself with different command-line tools, and still that's just scratching the surface.

Linux, on the other hand, has thousands of very useful programs that are run from the command line and therefore it may not be easy to find the help for that particular programs.