Acting is an essential part of a successful movie. The people playing the characters need to convince the audience that the emotions they are feeling are real. In order to do this they need to have spent a number of years training.
During the silent era the mannerisms used by actors were much more exaggerated. This was due to the fact that many of the people on screen were used to being on a stage and performing for large crowds. However, this form of acting did not translate well when it came to close up shots.
Acting styles changed with the advent of sound on screen. People now had to use their voices to further convey their character. This was an issue for some in the industry and a number of big stars failed to continue their careers.
Today acting on screen is much more naturalistic. Performers in Hollywood films are highly paid and celebrities to the public. The Academy Awards give out accolades for the best in this part of the industry. The ceremony is watched by millions each year and is used to determine the most successful movies released.