On a PDF you can define text sections for a signer to complete. This text could either be connected with the terms of the document or not - e.g. the signer ticking a checkbox to confirm they have read the document, or writing in their name would not be substantive to the terms of the document.
The distinction is important. If you have more than one signer, you don’t want to hold up the signing process while everyone waits for some text from another signer when that text is not connected with the terms of the document. Now you can define whether text is one type or the other by checking the ‘Part of terms’ checkbox for a signer text element. Untick this if other signers don’t need to wait on the text that goes here before they can sign.