French drains come in many different varieties. Here's a breakdown of what they are and their purpose.
Curtain drain - this is a concealed drain that is covered in soil with vegetation planted on top. They deal more with surface water instead of groundwater like the standard French drain does.
Filter drain - often used with a French drain, this type deals with groundwater alone.
Interceptor drain - used in city sewage systems or storm sewers.
Dispersal drain - a multi-disperse drain that distributes water from septic systems.
Fin drain - a subterranean pipe with an upward placement. They direct water to a traditional drain.