The term 'costume' refers to any clothing worn by actors in the course of a production. The costume department is responsible for this along with accessories, footwear, underwear, millinery and any other garments (http://www.bbc.co.uk/design/design_roles.shtml)
Costume is a quick way to suggest character. What clothes people wear and the way in which they wear them tells us a lot about their personality and perhaps quite a bit about their social background.
TASK
For each character in your script there should be a Character Bio. Using the bio as a starting point, create a mood board of photographs that suggest the kind of visual look and costume ideas that could be appropriate for that particular character. Don't limit yourself to a Google image search. Look on flickr.com as well as instagram, deviant art and elsewhere.
The mood board should be a collage of ideas and influences, a collection of snapshots that show a mix of stereotypical and individual takes on different looks and that demonstrates that you've thought about every aspect of costuming, from hats and jewellery down to what kind of shoes or trainers the character would wear and why. You can individually create a storyboard for each character or divide the characters up amongst different members of the group. It's important that each character stands out individually, even, as in the case of St. Trinian's they are supposed to be wearing the same uniform!