In a database, each record consists of fields. A record of a publication reference contains information about tracing the publication and information about the topic of the publication.
When you are looking for a topic, the most informative fields on a record are Title and Subject but also Abstract or even Full-text along with Source name.
Limiting you search term only to have occurred in a Title or a Subject –field will help to focus your search to the most relevant results.
A search term occurring in an Abstract might be relevant, but it can also be incidental. A lot depends on the context or on the term itself. Usually, it is wise to use several search concepts in order to define the specific aspect.
Example: You are interested in How dyslexia affects learning. You make a query:
dyslexia AND learning
As a result, both these records contain both terms, but the one on the left side is not related with your topic.
Example of a query utilising fields:
Watch a video (1:52 ) of Field searching by Wahlstrom Library. The link in the picture takes to Youtube: