Why does theater movie have black bars at the top or bottom.?

Is it needed.

Why does theater movie have black bars at the top or bottom.?performing arts show

Movie theater screens are rectangular and not square. Most shows are Pan Scanned and a lot is cut out of the show. Now, most DVDs come in letterbox and that cuts nobody out. The bars are there to turn your television into a rectangle.

Why does theater movie have black bars at the top or bottom.?opera cd opera theater

That means it is showing you exactly what was recorded. When They format it without the black bars, they cut out some of the shot.
When you watch a movie in widescreen, it shows the entire picture. Most movies are filmed in widescreen. Widescreen movies played on regular TVs don't fit the square screen, so the space not filled by the movie appears as black bars on top and bottom. Movies formatted for TV are called Pan and Scan or "Full Frame". These movies basically cut a square out of the rectangular widescreen shot and stretch it out to fit your square television screen. When you watch these movies, you only see a fraction of what was originally filmed. For example, in the movie "Ghostbusters" when the team arrives at their first job, Egon is cut completely out of the picture in the Pan and Scan version of the film, but you can see him in the Widescreen version.
Movie screens are rectagonal. TV screens are square. They shrink the picture down (using the black bars) so that you see exactly the same thing you'd see if you were watching a movie in the theater. It's called "widescreen" or "letterboxing."

This is the preferred way to view a movie, as you are seeing the entire image. Watching it "full screen" chops off the sides of the picture, causing you to lose as much as 50% of the image.

No true movie lover prefers full screen.