A Home Owners Association (HOA) (sometimes called a Property Owners Association or POA) is a quasi-governmental association having limited jurisdiction over development in a subdivision.
The HOA is formed at the outset of a subdivision development by the property developer, who controls it at the outset (and, thus, controls the ultimate development of the subdivision) until such time as there are sufficient property owners to take over the HOA.
HOA's are generally governed by state corporation law. The two key documents governing the HOA are the by-laws (which govern how the HOA operates, how its directors are elected, etc.) and the Covenants, Conditions, and Restrictions (CCR, which govern structures in the property: these are quite restrictive, covering everything from the minimum size of a structure, the type of structure -- for example, a CCR can prohibit mobile homes, to whether pets are allowed). The CCR's generally "run with the land"; therefore, a future property owner is bound by the CCR's even if the property is purchased well after the development is formed.
An HOA can provide only minimal benefits, or extensive ones such as community swimming pools and clubhouses. The benefits are paid for via mandatory HOA dues, which can be assessed monthly, quarterly, or annually. Failure to pay the dues can subject the property to foreclosure.