Quick View is a balloon showing an item's most important information. For example, in a service call form the Caller field points to a person item. With Quick View you find the most important information such as the caller's e-mail address in a balloon.
The following picture shows the Quick View balloon for the Caller field in the service call form.

TIP: If you frequently access the
Quick View balloon for particular fields, you may
prefer to have the Quick View information permanently displayed in
a show field such as the one illustrated in the following picture.
Contact your system administrator about setting show fields.