Perl actually stands for "Practical Extraction and Report Language," but you don't really need to know that unless you want to impress your nerd friends. Perl is a scripting language which uses a syntax simliar to C/C++. It is commonly used by Web programmers to create scripts for Web servers. Perl is especially good at parsing text, so programmers often use it for reading and searching through text files.
As a regular computer user, you won't get to see Perl in action, since it does most of its work "behind the scenes." Perl scripts are run on the server computer before any information is sent to your Web browser. Oh well, the code looks like hieroglyphics to most people anyway.