Fields - spaces in the document designated for signing and editing (filling in) by the recipient. There are different types of fields for different kinds of input: Signature Field, Text Field, Date Field, Formula Field etc.
What can you do with fillable fields?
Users can add or remove fields in the document and assign them to a particular signer. Fields can be marked
required in that case signers wouldn’t be able to send theit signed copies without filling in those fields.