This infographic from kitchenknives.co.uk should help you choose the right knife every time in the kitchen. It lists 12 knife types and what they can be used for, from the multi-purpose chef's knife to the more sparingly utilised paring knife.
You may already know much of this, but it can never hurt to brush up on your knife knowledge. If you're looking to get a little deeper into the world of knives, Tim Hayward's Knife - The Culture, Craft and Cult of the Cook's Knife is a great place to start. Hayward shares tons of advice on different knife types, how to buy a knife, and grips and cuts to perfect.