A colonia was a Roman outpost, usually established by veterans of a Roman Legion, who received land as a part of their retirement from the Legions.
Some examples would be
Modern uses
In Mexico, colonia is used for a neighbourhood. It's a frequent term in Mexico D.F. addresses.
Primarily Hispanic settlements along the U.S.-Mexican border are also called colonias. These are often substandard.
Colonia is also the name of a city in Uruguay.