The parts of each record or citation in an index or database are searchable. These parts are called fields.

When you search by a field, the computer will "look" only in that field when it looks through all the records in the database. It will try to match your search term.

For example, an

Author Search looks only in the author field

Title Search looks only in the title field

Subject Search looks only in the subject heading field

Date Search looks only in the date field

But . . . a Keyword Search looks for items anywhere in the record. It is the broadest search.