My previous posts contained many links to the Hyperspec, but to restate explicitly...
There exists such a concept as
technical documentation. It is a body of text which explains in a, hopefully, systematic, exhaustive and detailed manner how a system woks and how you are supposed to use it.
For Common Lisp the most important piece of technical documentation is the ANSI standard. There is an online hyperlinked version available at
http://www.lispworks.com/documentation/ ... /index.htm. The contents are grouped by
chapters, and there is an
index. Using either you can find documentation for function
MEMBER, which, among other this, lists all the arguments the function takes, what type they should be and what they do.