Description

An attachment is a files or media object that the user provides in association with an activity.

There may or may not be a meaningful relationship between the activity and the attachment, and the user may associate zero or more attachments to an activity.

Purpose

The attachment(s) of an activity acts as a generic bundle of files and media objects that the user wishes to associate with an activity. Depending on your case and the actor, activity verb, activity object-type, or attachment object-type you may wish to display an attachment as a single link below an activity, or as a thumbnail or inline representation, as in a video or audio file.

An attachment is equivalent to an Atom enclosure, except that it bears several additional properties that are not provided by an the enclosure element.