Like nearly all of the most coveted antiques these days, a dresser was designed originally as a purely practical piece. In the days before fitted kitchens with corner cupboards on fancy pull-out rails and ceiling height cabinets for storing an extensive collection of plates, there were simply dressers, butcher's blocks and open hearths for all your culinary needs. A dresser was where you stored plates, glasses, cutlery and linens, and that use remains today. The difference is, however, that mostly, dressers are now extras on top of all our kitchen cabinets and so they are more decorative than practical.
In the UK, dressers are known as Welsh dressers, unless they're from Ireland in which case they're Irish. Essentially though, they are quite similar and a Welsh dresser doesn't actually have to come from Wales. Confused? Ignore the minutiae and focus instead on how to use a kitchen dresser. Now that we have ample space elsewhere in the kitchen for storage, the best use of a dresser is to display a collection of pretty ceramics or antique glassware on the top, open half, while shoving kitchen appliances, tablecloths, children's crockery and all those other unsightly items in the cupboards on the lower half.
As for the sideboard, dress it up with a frilly lamp, an endless supply of fresh flowers or perhaps an enviable collection of lustreware jugs featuring pastural scenes and your kitchen will be the most coveted room around.