RTL mode vs. LAND modes?

I’m looking for some clarification on what LAND mode is/does?
Does it require GPS?
Does it work either way with or without GPS?

And I guess RTL is RTL and land if a parameter is set to zero.

Thanks.

Still confused:

A s (Y) Reduces altitude to ground level, attempts to go straight down

A= Automatic control

s= “Pilot controls climb rate” (how does this work when landing? and how is this “automatic”?

(Y) *not “Y” for GPS and no description what “(Y)” means as opposed to “Y”

http://ardupilot.org/copter/docs/flight-modes.html

If there is GPS lock when Land is enabled it will Land at those coordinates like RTL does. If no GPS it will Land while drifting in the wind.