I assume you are a man, who is crossdressing.
There are many different kinds of cross-dressing, and many different reasons why an individual might engage in cross-dressing behavior. The following examples are by no means an exhaustive list.
Some people cross-dress as a matter of comfort or style. They have a preference in clothing which is only marketed to or associated with the opposite sex. In this case, a person's cross-dressing may or may not be visible to other people.
Some people cross-dress in order to shock others or challenge social norms.
Both men and women may cross-dress in order to disguise their true identity. Historically, some women have cross-dressed in order to take up male-dominated or male-exclusive professions, such as military service. Conversely, some men have cross-dressed in order to escape from mandatory military service.
Single-sex theatrical troupes often have some performers cross-dress in order to play roles written for members of the opposite sex. Cross-dressing is often used for comic effect onstage and onscreen.
Drag is special form of performance art based on cross-dressing. A drag queen is a male-bodied person who performs as an exaggeratedly feminine character, in an elaborate costume usually consisting of a gaudy dress and high-heeled shoes, heavy makeup, and a large wig. A drag queen may imitate famous female film or pop-music stars. A drag king is the counterpart of the drag queen — a female-bodied person who adopts an exaggerated masculine persona in performance or who imitates a male film or pop-music star. Some female-bodied people undergoing gender reassignment therapy also self-identify as drag kings, although this use of "drag king" is considered inaccurate by some.
Many transgendered people cross-dress relative to their birth sex, but transgendered people who have undergone gender reassignment therapy are usually not regarded as cross-dressing.
A transvestic fetishist is a person (typically a heterosexual male) who cross-dresses as part of a sexual fetish.