What Is The Role Of A Costumer Designer?

I wish to go to University to become a Costume Designer. But, I myself actually don't fully grasp what the role of a Costume Designer is, hence I want to post about it.
According to wordnetweb.princeton.edu/perl/webwn costume is defined as "the attire characteristic of a country or a time or a social class". Therefore costume design is the envisioning of such clothing for a character. Costume design is used in entertainment such as dance, theatre, film and opera. 

The costume for a character is representative of their person including personality, gender, age, style, social status, occupation, place of habitation, mood etc. The costume can distinguish minor and major characters, relationships and changes in characters. It also enables performers to emotionally and physically portray their characters accurately. It must also be comfortable, flexible and durable for practicality. 

 The costume is intended to make a visual statement to the viewers. The costume is intended to seamlessly merge into the production as there is communication with the director, lighting designers and set designers.

The Costume Designer starts by understanding the concept and story of the production. If there is a historical setting, the appropriate fashion must be researched and referenced. Rough costume sketches are presented to the director and design team. Once affirmed, the final designs are composed. Also, the number of performers requiring costumes including those without vocal roles. 

A costume plot is required. This is a diagram or list of the number of performers in each scene and their movement. This enables the understanding of how many costume changes are required. 

Obviously there is more to costume design than I have covered, but this is the basis and this will help me create my portfolio for my University application for Costume Design. This is to aid me on my journey.

Afshan

Bibliography:
http://www.aact.org/people/costumedesigner.html
http://en.wikipedia.org/wiki/Costume_design
http://www.artsalive.ca/collections/costumes/designer_role.php?lang=en