The term "update field" refers to a type of step that can be incorporated into your automation (a.k.a. drip campaign).
The update field step is unique as it allows you to change a contact record based on behavior in the automation. Update Field will add a value to a contact’s demographics or add them to a category defined in the step.
Drag the Update Field step over to the desired section of your workflow. Click the pencil to set your update specifications:
If applicable, choose the category you wish to add the contact to from the list (the category must already exist).
If you would like to update a demographic field, click 'Insert Field' and add the necessary text. You can do more than one.