What is focus?

[Murray Cumming Comneon com]

Hopefully this is in a document somewhere and you can just point me to it?

What exactly is the purpose of the "focus" for accessibility, as compared to
the selection. For instance, in a TreeView (for instance Nautilus), I can
select an item, or I can move the focus to an item while the selection does
not move. Is that just a way to read the other items before I've decided
whether I want to actually select it? Would it be the focused thing that
would show up on a braile display, for instance?

Murray Cumming
www.murrayc.com
murrayc usa net