The most commonly used anchors are called

Marker

and

Content

anchors. These anchors are often used as a pair:

To understand these anchors, imagine a printed questionnaire. The first line typically asks for the person's last name and first name, with each label followed by a blank space to receive the information. The printed labels

Last Name

and

First Name

are

Marker

anchors, and the blank spaces are

Content

anchors. The anchors provide a means to home in on the data and extract it from the source document.