IBM developerWorks has an article that goes over many of the symbols you’ll encounter at a Unix/Linux/Mac OS X/Cygwin command line:
You’ve learned a few of the basic commands to help you maneuver through a directory structure, create and modify files, see what processes are running, and maybe even administer users and the system. That’s great, but you want to understand what the UNIXÂ® administrators next to you are typing. It looks like a lot of commands interspersed with strange symbols. Learn what |, >, >>, <, <<, [[ and ]], and many more symbols mean in UNIX and LinuxÂ® as well as how to get the most out of operators such as &&, ||, <, <=, and !=.