A home warranty policy protects you from the expense of major repair or replacement caused by unexpected mechanical failure of a major system or appliance. For a moderate premium (usually in the $400 range for a basic policy) payable at closing, you can acquire a policy which protects your for one full year after closing from major repair or replacement bills.
Most policies have a $50 to $100 deductible, and you usually must call through their people for repairs. The age of the home should be a consideration as to purchase a warranty or not - a 15 year old home with original equipment versus a two year old home. Several companies offer these policies.