Definition: Attachment or File Attachment is a file that has been attached to an email. It can be any file type, such as a document, photograph, image, audio file or any other file that may be accepted by an email program.
A file attachment may also be a computer virus sent by a hacker so it is extremely important to know who the sender of the email is and what file type extension you are trying to open. Be cautious with file types with the extension of .exe as this is an executable file and can sometimes be a virus that may harm your computer.