What are DUDV maps?

I’ve seen a few on the web, but no information can ever be found by me about them, and they look like this:

I hope this is off-topic enough not to get closed by a moderator.


Its for GPU pixel and vertex shaders.
The map you postet is for water.
dU/dV is the correct spelling…
Its a derivation of a normal map (d[something] in math)

Its a mix of a normal map and a refraction map.