The UK Annual format is not typically found in North America. These are hardbound collections, produced at the end of each year with the cover date for the following year. Presumably they're aimed at the Christmas market. The majority of the material is reprinted comic stories, usually a couple of comics worth - often two consecutive stories, but not always. There's also usually an original text story, and some puzzles and games.
See also Spider-Man Annuals (UK Movie).