FORM FOLLOWS FUNCTION

Form follow function is the principle is that the shape of a building or object should be primarily based upon its intended function or purpose.

For designers, form is the elements that make up our designs, our pages. Function is the objective of the design whether it is a sign giving directions or a book that entertains with a story.

In print design, form is both the overall look and feel of the page as well as the shape and look of the individual components - the typefaces, the graphic elements, the texture of the paper.Form is also the format whether the piece is a poster, a tri-fold brochure, a saddle-stitched booklet, or a self-mailer newsletter.

Function
For designers, function is the practical, getting down to business part of the process of design and desktop publishing. Function is the purpose of the piece whether it is to sell, to inform or educate, to impress, or to entertain. It includes the copywriting message, the audience, and the cost of getting the project printed.

Form and Function Working Together

Function needs form in order to accomplish its goal. Form without function is just a pretty piece of paper.

Function is deciding that a poster plastered around town would be the best way to inform the general public about a band's upcoming club performance. Function is specifiying how much the band can spend on that poster. Form is choosing the size, colors, fonts, and images based on the function and arranging the text and graphics so that the poster attracts attention and looks good.
To practice the rule of form follows function, start the design process by first getting as much information as possible about the purpose of the piece you are creating.



source: http://desktoppub.about.com/od/graphicdesign/a/formfunction.htm