curious as I don't recall the video (in the FAQ) mentioning flats or workhorses, but from what I can gather from reading other posts they seem like they might all be similar things?
To add to AFwifelife's awesome pictures: a prefold has lots of layers to it, more in the middle than the edges, they come in a few sizes. A flat is a single layer that you need to fold to fit your baby, different folds put the layers in different spots and have more/less layers. Truely one size from birth to potty learning. A workhorse is like a prefold cut and sewn into a fitted diaper. They are available with snap closures or without closures. You use pins or a snappi/boingo to secure all three (except a workhorse with snaps). All three need a cover over top.
ETA: I'm a slow typer and this answer was unessessary.
Re: prefolds/flats/workhorses- are they all the same thing?
Workhorses are made by Green Mountain Diaper and they are a fitted diaper.
ETA: I'm a slow typer and this answer was unessessary.