User-created media content is being increasingly shared with the communities people belong to. The content has a role of a motivator in social interaction within the communities. In fact, the content creation and management can be often seen as a collective effort where group members participate to create common memories and maintain relationships. We studied how four communities interact with content that is collectively created and used, i.e. collective content. The aim was to explore communities' collaborative interaction activities and the purposes of the content to be able to specify what collective content actually is. We report users' motivations for creating the collective content and its role in community interaction. We determine the factors and characteristics by which collectivity (i.e. the extent to which something is collective) of the content can be described: the community's contribution, the relevance of the content and the level of sharing. Based on th...