Superhero

A superhero is a stock character that battles crime and injustice. However, despite the name, by most people's definitions, to be a superhero you don't need actual powers. Sometimes these heroes are referred to as costumed crime fighters. A female hero is often called superheroine.
Common Traits

• Extraordinary Powers and Abilities- Almost all superheroes possess an extraordinary power / abilities. This range from “normal powers” like kung fu skills to super powers like heat-ray vision.
• Strong Moral Code- Usually includes a willingness to risk one's life for others and an unwillingness to kill.
• Motivation- Superhero motivations range from a sense of responsibility (Spider Man) to desire for vengeance against crime (Batman).
• Secret Identity- Used to protect the hero's friend and family. It has decreased in popularity due to the Fantastic Four.
• Distinctive Costume- See Common Costume Features
• Supporting Cast
• A Job with Minimal Supervision or Being Insanely Rich
• An HQ
• Origin
• Weakness- The Achilles' heel of the hero.

Although most heroes like to be solo, sometimes heroes will form a team. Also, sidekicks have decreased in popularity.

Common Costume Features

• Mask- Hide's the heroes' face hence protect their identity. Some heroes wear helmets instead.
• Symbol- A visual icon for the character (ex: Superman's S, the Fantastic Four's 4)
• Form-Fitting Clothes- Often referred to as spandex, but some heroes predate it's creation.
• Some times the costume has functional use (Batman's utility belt)

Despite being closely associated with superheroes, few heroes wear capes and a majority don't.
Headquarters
Usually, superhero HQs have several common traits:

• A safehouse to protect themselves
• Laboratory
• Research library
• Armory
• Communication Center
• Garage / Dock/ Hangar
• Defenses for the HQ
• Trophy room
• Medical Center
• Common Area to hang out

Trademark Status
Despite the fact the term “super hero” is used generically, DC Comics and Marvel Comics jointly join the copy right to the term. However, some people argue that it does not met the legal status to be copy righted, and as such, it is a “misuse of trademark law to chill competition”.
References:
http://en.wikipedia.org/wiki/Superhero
http://upload.wikimedia.org/wikipedia/commons/0/0b/Fleishersuperman.jpg