The drains are different. Go to Definition of Hydrologic Term, and press 'C' to get a definition on Curtain Drain and 'F' to get a definition on a French Drain.
If you would like to read a little about Into to Landscape Drainage, go there and then there's a link for How To Construct A French Drain. The only difference I have with the latter article is they suggest you use landscape fabric (which is different from Weed Block.) Sometimes, folks confuse the 2. I prefer to use Filter Fabric. BOTH can be 'had' at a Quarry, or a Stone & Gravel yard. Check your Yellow Pages.
If you need more info, e-mail me directly. My best to ya and hope this helps.