If something breaks on your computer, you want a good warranty from the manufacturer. A standard warranty is usually one year, but for laptops we recommend an extended warranty due to the increased risk of moving laptops frequently. Normally, warranties on computers do not cover breakage from drops, drowning, etc., but in some cases, accidental damage protection can be purchased as well.
Also, computer manufacturers will often allow the purchase of an extended warranty for some time after you've bought the machine. Ask to be certain.