A Text field is like a string field except that it's a large box instead of a single line. You can change the size of the field by adjusting the Rows and Max Length parameters.

Rows controls the vertical height of the text box. Max Length controls the number of characters the site visitor can input at a time. If you want to limit a Comments text box to short comments, you might choose 500 characters as the limit.

The Default field can be used if you want to suggest some content to the site visitor or wish to show an example of the sort of information you want from them.

You can also Reject Text with Links to discourage people from adding links to your text area field. One reason why you might choose to do this would be if you're asking someone to enter some information and you don't want them to simply link to a blog entry or other online content.