Sometimes the term costume can refer to wardrobe and dress in general, or to the distinctive style of dress of a particular people, class, or period of time. It can also refer to the artistic arrangement of accessories in a picture, statue, poem, or play, appropriate to the time, place, or other circumstances represented or described, or to a particular style of clothing worn to portray the wearer as a character or type of character other than their regular persona at a social event such as a masquerade, a fancy dress party or in an artistic theatrical performance. There are many events that occur during the year that offer one the opportunity to wear a costume including Halloween and Mardi Gras.

Theatrical costumes for plays and operas, in combination with other aspects, serve to portray characters' age, gender role, profession, social class, personality, and can even reveal information about the historical period/era, geographic location, time of day, as well as the season or weather of the theatrical performance. Sometimes theatrical costumes literally mimic what the costume designer thinks the character would wear if the character actually existed. On the other hand, often stylized theatrical costumes can exaggerate some aspect of a character. Without theatrical costumers, the audience would be left wondering who is related to whom, and which person is which. Costuming truly is as important as the set and the script, yet most audiences take it for granted.

Costumes can also represent a nation or region expressing local (or exiled) identity and to emphasize uniqueness. It is often a source of one's National pride. Probably one of the first things you would think of would be a Scotsman in a kilt or Japanese in a kimono.

The wearing of costumes has become an important part of Mardi Gras and Halloween celebrations, and (to a lesser extent) people may also wear costumes in conjunction with other holiday celebrations, such as Christmas and Easter. Mardi Gras costumes are usually jesters and other fantasy characters, while Halloween costumes traditionally take the form of supernatural creatures such as ghosts, vampires, and angels. Christmas and Easter costumes typically portray mythical holiday characters, such as Santa Claus by donning a santa suit and beard or play the Easter Bunny by putting on a furry costume and head. Costumes may serve to portray various other character themes during secular holidays, such as an Uncle Sam costume worn on the Independence day for example.

One of the more prominent places people see costumes is in theatre, film and TV. Another very popular place for costumes is sporting events and college games Those costumes are called mascots. These team mascots help the club or team rally around their own teams cause. These mascots are a great source of entertainment.