What's the difference between a workspace number and a personal Caller ID?

A workspace number is an active line that can both call and be called; a personal Caller ID only shows your name/number on outgoing calls and can't receive calls itself.

Under Numbers, you see the distinction right away: a workspace number (bought from Telsmart or brought over through porting) shows up as a full, active line. A verified Caller ID is listed separately under "Verified caller IDs", with the note that it only works outbound.

Number detail with the "Outbound only" notice for a verified Caller ID.

Good to know: the Call routing tab is grayed out as long as a number is only a verified Caller ID — there's nothing to route, since nothing comes in.