Search engine keyword results

[allwayslearning]

Time after time when I see keywords used by people on various search sear engines that people used to come to my site, when I try to search with those terms my site does not come up in the first few pages of the particular search engine. What is happening?

[websiteideas]

The serps are constantly fluctuating. Do you notice them on the next page?

[allwayslearning]

Yes sometimes I do and have found some are not listed in a way I coudl have listed them so I did not realize they were there. Please tell me what serp stands for.