“A title sequence is the method by which cinematic films or television programs present their title, key production and cast member, or both, utilizing conceptual visuals and sound. It usually follows but should not be confused with the opening credits, which are generally nothing more than a series of superimposed text”.
Film-makers at the beginning of the 21st century have many options open regarding title sequences. Some films superimpose opening credits over the opening scenes, while others elect to do away with titles entirely, instead including elaborate title sequences at the end of the movie.
Many films have used unusual and fairly elaborate title sequences since the 1930s. In the 1936
Show Boat little cut-out figures on a revolving turnable carried overhead banners on which were displayed the opening credits This opening sequence was designed by John Harkrider, who created the costumes for the original 1927 Broadway production of the musical.
In general, a television title sequence will at some point badge the show with a typographic logo. Around this key element can be incorporated shots of highlights from earlier episodes or shows and key presenters' or cast members' names. Musical accompaniment can be either instrumental or a song and aided by the visual treatment of the images helps to convey the tone and mood of the programme.
http://en.wikipedia.org/wiki/Title_sequence