Every time you watch a movie, you are hearing the work of many people ib the background. Here are the facts. The normal cine-camera is capable of only recording sound in a mono(??) format, and that too not very clear. So comes the use of dubbing theaters, where an Automated Dialogue Editor(ADR) assists the actor to give life to thier characters.
Then comes the biggest drain on the system- The Foley Effects. Foley effects are all the side effect sounds that you hear, for ex: sound of footwear, sound of thunder, door open, door close, background noise. It is typically esitmated that for a single sequence, there could be atleast 16/24 tracks of foley effects alone. On top of this comes the background music and the voice. This is done on software like the Avid/ Pro Tools etc. Pro Tools by the way is the standard for mixing studios around the world. Every block buster that you hear/see comes edited off this system.