BIT ATTACHMENT is a type of computer file that is attached to an email or other electronic communication. It is usually a document, image, video, or audio file that is sent along with the message. The REIN and MEGA solutions refer to two different types of bit attachments. REIN stands for Rich Electronic Information Network, which is a type of bit attachment that is used to send large files over the internet. MEGA stands for Multi-Exchange Global Attachment, which is a type of bit attachment that is used to send multiple files in one email.