Search
Search from the application header looks across deals, people, organizations, and leads at once.
Results are grouped by record type, so a company name that matches both an organization and several deals shows both rather than burying one.
Selecting a result opens that record.
Visibility
Search returns only records you can see. It is not a way around visibility groups, so a colleague finding a record you cannot find is a visibility difference rather than a search fault.
Filters versus search
Search is for finding one known record quickly. For repeatable questions across many records, build a filter and save it. See Saved filters.