If the title of your field could use a longer explanation, you have the option of adding a more detailed field description to each of your fields. To add a field description, click on the dropdown arrow in the header of the field to which you wish to add a description, then select the "Edit description" option.

This will bring up a dialog box in which you can type a short description of what kind of information the field contains. When you're done, click the blue "Save" button.

Now, whenever you mouse over the information icon in the field header, your description will appear.