Velma from Scooby-Doo is usually considered to be the brains of the outfit. Her full name is Velma Dace Dinkley, and she is a fictional character in one of the most loved and watched animated television series, Scooby-Doo, which is about the adventures of four crime-solving teenagers and their Great Dane, Scooby-Doo. Velma is considered to be the most intelligent in the group and often makes great use of her skills in such areas as reading Chinese or Japanese, deciphering scientific formulae, operating communications equipment, and so forth. A running gag of the series is Velma’s trouble with keeping her glasses on her face. Velma is very nearsighted, and her glasses are usually accidentally knocked off her face while being chased by the villain. Her character is famous for the lines “Jinkies!” and “My Glasses! I can’t see without my glasses!”
When Scooby and Shaggy are too afraid to volunteer for a mission, which tends to be most of the time, Velma often offers them a dog treat called a “Scooby Snack” as a bribe. Another somewhat running gag is that she is actually stronger than she appears, often able to carry Shaggy and Scooby in her arms and still be able to run. And on occasion she’s able to carry Daphne and Freddy too, managing to carry all four, still able to run, and mysteriously know where she is going all at the same time.
Early in the series, Velma was occassionally shown to be somewhat sharp-tongued, a disciplinarian, especially towards Shaggy and Scooby. Velma has also been shown to be one of the braver souls of the group, not afraid to physically attack a bad guy like when she kicked The Creeper in the knee.
Velma is recognized by her famous orange sweater and glasses. When the gang splits up, Velma usually goes off with Fred and Daphne but sometimes goes with Scooby-Doo and Shaggy and on occasion, even by herself. As far as the group dynamic goes, Velma is usually the one who solves the mystery while Fred sets up the trap to catch the criminal, though the earlier episodes generally show the two of them working together, and sometimes the entire gang working as a detective team, leapfrogging over each other to solve the mystery. This dynamic has been exaggerated in recent portrayals to the point where Velma is the sole brain of the outfit.
References: Wikipedia