The words retention pond and detention pond are often used interchangeably, though there is a big difference between the two.
A Detention Pond is designed to hold rain water temporarily. It will hold the stormwater and slowly release it from the subdivision property. When it is not raining, the detention pond will often be dry.
A Retention Pond is designed to hold rain water indefinitely. It is not intended to release the stormwater from the subdivision property. The water is designed to be held until it evaporates and, in some circumstances, leaches into the ground below. It will often have water standing.