Bottom Bracket (BB) shell tapping (for f**ked threads)

I thought facing was making sure that the faces (hence the assumption on my part) of both sides of the bottom bracket shell were parallel?

Likewise I had assumed that passing a tap through the threads of the bottom bracket to make sure they were cut correctly/empty of corroded on crap was to tap the bottom bracket?

What is re-tapping a bottom bracket?

you are correct sir