Definition - What does Email Signature mean?
An email signature is a block of text appended to the end of an email message which often contains the sender's name and contact information. An email signature often contains a name, business contact information, email address a website URL, etc.
Techopedia explains Email Signature
Most email clients can be configured to automatically append an email signature to the end of of each email message. Some users make use of the signature to sign off the email message with funny quotes, conclusions, or other eye-catching messages.
Generally speaking, an overblown email signature not only annoys other users, but it clogs up correspondance with useless info.