SERPs

SERPs are "Search Engine Result Pages"

If a search engine user types in a search for "rubber baby buggy bumpers" and your web site is the first result, then you can be said to have the #1 SERP for "rubber baby buggy bumpers."

The whole purpose of Search Engine Optimization (SEO) is cause web pages to rank highly in the SERPS. The higher your web pages rank in the SERPS for their chosen keywords, the more traffic your web site will receive.

Tracking SERPs

Check How can I track my ranking in Google or other search engines? to find pointers to web-based tools for tracking your SERPs.