Editor level required: Beginner
Searching Pages is an effective means of finding out if pages are already made on a topic, or if you have a page very similar to a topic. Searches, however, by default, only search the main pages. In "my preferences", you can choose to search other areas. But, if you want to search everything for one specific query, use "all:" as prefix and it'll work.
This is an example of a search: