With the purchase a house, you own the building and the land your building. With the purchase of a condominium the ownership differs in that you have exclusive right to the interior space of the unit you purchased (you may also have a small outdoor space); the outside space, grounds shell of the building, and common areas are owned by the condominium corporation and are shared spaces among all unit owners.
Additional monthly fees are payable by unit owners to the condominium corporation to account for upkeep of common areas and a reserve fund is established for maintenance and repairs to the building.