Those functions are meant to draw 8*8 monochrome with fill bits bitmaps -- like game sprites -- on the VRAM.
Function with the _cl suffix are functions using clipping, which means they are able to draw sprites even if they aren't completely on screen. Other functions only draw the bitmap if it is in the screen -- which makes them a little faster.
For bitmaps with other dimensions, please see ML_bmp_or(3) and ML_bmp_16_or(3).