A flat board usually covered with an ironing board cover on which clothes are laid while being ironed.

Purpose:
To keep the clothes flat while the the wrinkles are ironed out. Try ironing on a bumpy surface and you'll be praising the ironing board.

Shape:
Ironing boards (as far as I've seen) are usually shaped like a stubby crayon. The pointy end works out nicely for shirt sleeves and pant legs.

Types:
I've seen 3 major types of ironing board. Short-legged boards for table tops or counter tops. Long-legged boards for standing on the floor. And ironing boards that fold out of a closet or down from the wall. I've only seen this last type in comedies and cartoons, but they seem to be quite dangerous.


Here's my ASCII interpretation of a long-legged ironing board:
   ______________ 
 /'              |
(                |
 \.______________|
    \\. //\\ .// 
 m1a `\\.  .//.  
    // `\\//  \\ 
   ||  .//\\.  ||
   ||.//   `\\.||
   |//       `\\|
   ''          ``