Denise is the video output chip or VDU in the Amiga. It reads bitplane data from memory and combines the bits into color numbers, and then looks up the RGB value to output to the screen from the palette in the custom chip registers.
This pixel output takes place at three rates or horizontal resolutions: lores, hires, and super-hires.
Doubled vertical resolution is also possible by interlacing odd and even scanlines at half the framerate.
Apart from this standard mode, Denise also operates in pseudo-64-color mode (Halfbrite or HBR) and pseudo-high-color mode (Hold-and-Modify or HAM) mode.