Multisession

[neoiv]

When burning dvd's it asks if I want to use multisession. What does this mean? Also does it affect how I view the video. Currentely I cannot find the menu on the movie The Forgotten, on the other movies I have had no problems. Suggestions? Thanks
Also I cannot get to the beginning of the movie (The Forgotten) it seems I have every language downloaded and the directors commentary.