ToggleBackgroundTableAddress

The NES 8kb graphics ROM image consists of two parts: two 4096 byte images each consisting of 256 8x8 chars. Let's say the first image is "bank 0" and the second is "bank 1".

ToggleSpriteTableAddress(N) will tell the PPU that sprites are located in bank N, where N is either 0 or 1.

Similarly, ToggleBackgroundTableAddress(N) where N is 0 or 1 will tell the PPU that the tile image is located in either bank 0 or 1.