I do not know what "Bitwalk Through" means.
But to test a digital circuit we often move or walk a bit from one pin/signal to the next. For example if you were testing a circuit on a uC port you would first make bit 0 hight, then bit 1, and continue till you activated and check all bits. The check can be done by hand with a variety of tools or automated using a test fixture.
As each bit is made high you also test other bits to ensure they are not shorted to it, if they move or try to move with another bit.
There are several other tests that are helpful like making odd bits 1 and even 0 the switching them. etc etc
Does that help.