tambour beading is a french technique where you use a hook to "stitch" beads onto fabric that is stretched over a frame. the hook looks like a little needle. like this:
so when you bead you are actually stitching on the back side of the fabric. the beads are on a thread that you catch with the hook. generally you hold the bead in place with your finger and pull the thread through. its like making a chain stitch but with beads on the front. its entirely by feel. does that make sense?
here's a diagram of it:
7.jpg (image)
this is a dress i made for my dawls. the beads are in clustered flowers all around the dress. it has embroidery too:
so all that beading you see at lacroix

and chanel is done in the tambour technique.