What is the difference between an internal signer and external signer?

Internal signers are WebForms users who have been set signing authority permission, by the WebForms firm Administrator. Because internal users are already verified through WebForms, they do not require an SMS passcode as validation. An external user is a signing party that exists outside of WebForms. External users are required to enter a passcode sent via SMS into their email to be able to access the document for signing.