A homeowners policy is split into several different coverage types which usually each have their own separate limit (although they might be determined as a percentage of the coverage A limit):

Coverage A is the home itself.
Coverage B is additional structures on the property (a detached garage or shed for example).
Coverage C is contents (furniture, computers, clothing, etc) and includes coverage for the theft of items even when not in the home (e.g. getting a laptop stolen out of your car).
Coverage D is living expense (staying in a hotel while your home is rebuilt following a fire).
Coverage E is personal liability.
Coverage F is medical expense (meant to cover small injuries to visitors to your property without needing to determine fault/liability).

The first three can be either on an Actual Cash Value or a Replacement Cost basis. Blueaussie's link gives a good explanation of what the difference is and how Replacement Cost works in practice. Replacement Cost will always result in equal or higher payments in the case of a loss and so it will always be more expensive to buy.