This enables tile blitting. Tile blitting is a drawing technique
where the screen is divided into rectangular sections (tiles), whereas
the standard blitting divides the screen into pixels. Because the
default drawing element is a tile, drawing functions will be passed
parameters in terms of number of tiles instead of number of pixels.
For example, to draw a single character, instead of using bitmaps,
an index to an array of bitmaps will be used. To clear or move a
rectangular section of a screen, the rectangle will be described in
terms of number of tiles in the x- and y-axis.

This is particularly important to one driver, matroxfb. If
unsure, say N.