Utattemita Tours are events on Nico Nico Douga where one person invites several Utaite to sing songs with a certain theme, usually a genre.
On the first day of the tour, the tour host uploads an "Opening" that introduces the theme and the participating utaite. Other covers are then uploaded all in close succession, along with an "Ending" that summarizes the tour and thanks all the participants.
"Albums" are similar to tours in that they are collections of themed songs from various utaite, but are different in that the theme is usually the current season.