To define a "diverse" actor, it is someone who can play just about any part and do a fantastic job in any role they assume. The key is whether or not they are actually good at it because there are plenty of actors out there who try to partake in roles that aren't suited for them and the film suffers in result.
This leads to the other side of the coin, the "stock character" actors. These are the actors who are really good at playing a certain character type and always perform in that one niche. When they do try to depart from what they are naturally good at, it can sometimes seem awkward or forced.
Types of stock characters vary from the goofy sidekick, the bad guy you love to hate, the charming hero, the beautiful babe, and so on. There are many different categories that can be further broken down, but just think of the typical microcosm that you find in a movie (hero, bad guy, damsel, comic relief, etc) and draw from that.
Sometimes new actors or actresses who are trying to find their stock character role will try his or her hand at a variety of different parts to see which suits them best. For those who tend to be successful in each of their positions will typically continue on to remain a diverse actor or actress and never settle for one particular kind of character.
An example of an actor who is diverse is Johnny Depp. Depp has been a pirate, a gangster, a mad hatter, a greaser, a barber, a tourist, a chocolate maker, and lately the Native American, Tonto in "The Lone Ranger." These are only a few of the many roles he has immersed himself in, but every single part Depp is able to fully become that character and his versatility shows.
|A few of the many faces of Johnny Depp|
An actress who could be just trying to find her niche, but is doing a great job so far at being varied in the roles she chooses is Anne Hathaway. Starting out as a sweet and innocent nice girl in "The Princess Diaries," Hathaway has moved on to playing a personal assistant in "The Devil Wears Prada," a spy, a competing bride, the White Queen, Catwoman, and most recently Fantine from "Les Miserables." It is obvious that Hathaway is trying to prove a point that she can play gritter parts than just the pretty girl-next-door type.
Christoph Waltz, though only starting his fame in 2009, is a stock character actor. It was his part in "Inglorious Bastards" as the dreaded Jew Hunter that caused him to become well-known and be a perfect bad guy for several other movies. Waltz is able to repulse the audience when in character in such a way they will always despise him. He is the antagonist in several films such as "Water For Elephants," "The Green Hornet," and "The Three Musketeers."
Scarlett Johansson's stock character is the beautiful girl. She always plays an attractive woman who uses her looks for various reasons. In "Iron Man 2" and "The Avengers" Johansson is the seductive spy, Black Widow, who uses her looks to get her in the right places to snoop. In "The Prestige" she is the magician's assistant and helps double cross one for the other with her looks again. The point is that most characters that Johansson plays focus on their looks and that is what she is able to bring to the table.
Now keep in mind there is nothing wrong with either one of the types of actors. This is simply a way that I categorize them in my mind for simplicity's sake.