Take a look at the photos above. Both are scene clips from the film, King Kong. What are the obvious differences? The 1933 version of King Kong was a puppet type figure while the 2005 version was built and operated by motion sensor by actor Andy Serkis. The techniques used today are more complex than the techniques used in special effects for earlier films and TV. Today, special effects make the visuals appear more realistic and engaging. However, at the time, the earlier techniques did the same for audiences of the earlier generations.
The Hollywood studio is well know for its use of special effects in films and TV series. Seeing is believing, and if the film makers want audiences to believe that there is a 50 foot woman walking around taking vengeance on men (Attack of the 50 Foot Woman, 1958), a muscular cyborg from the future set out to destroy an unborn child (The Terminator, 1984), astronauts who travel to the far future to a world where primates rule and humans are inferior (Planet of the Apes, 1968), or a boy who discovers he's a wizard and that there is a whole world of magic (Harry Potter, 2001), the special effects will make you believe it...or at least attempt to make you believe.
Early types of special effects include stop-action, rear projection, and front projection. Imagine that a character was going to leap unto a tree. The camera would stop as the character appeared to go into a leap and start again, giving the character enough time to actually be placed on the tree. This is called stop-action effect. Rear and front projection allows the characters to be placed in the foreground of an image or infront of the image to look as if they are a part of it (Media Now).
Later types of special affects were largely computer generated. Green screen and motion capture are techniques largely used. Imagine blades being thrown at a character and stabbing him gruesomely. With green screen, the blades could be computer generated and the actor would be placed in front of the green screen and later placed in the sequence to appear as though he was actually there. With motion capture, an actor would use sensors to be connected to the computer assembled being and the sensors allow the actor to play out the motions for the being (Media Now).
With special effects, all sorts of films and TV series were and are possible. Special effects took over the aging process instead of different actors playing younger/older versions of characters, different worlds and creatures can be made, death scenes are more gruesome, comic-book superheroes become live-action, explosions become more extreme, and magic can be made. Special Effects add more to audience imaginations and broaden the minds of viewers. The Hollywood studio system continues to evolve special effects, now with the '3D effect'.