Thanks, that cleared it up for me.Batman focuses on Batman himself. Ships twice monthly.
Detective Comics (also known as 'Tec) is more of an ensemble cast, although the roster has changed since the Rebirth run started. Ships twice monthly.
Batgirl is about Barbara Gordon as Batgirl. Ships monthly.
Nightwing is about Dick Grayson as Nightwing. His previous title, Grayson, would be a good read for background on this Nightwing run and shares one of the writers Ships twice monthly.
All-Star Batman doesn't really factor into the main continuity. Ships monthly.
Batgirl and the Birds of Prey is the team of Barbara Gordon, Black Canary and Huntress. Ships monthly.
There's an upcoming Batwoman title, spinning out of Detective Comics and focusing on Cassandra Cain
Just something you should note, Batman, Nightwing and 'Tec did a crossover a few months ago called Night of the Monster Men. The Monster Men issues will only be collected in an event trade and won't feature in the trades for the individual titles. The first set of trades for Rebirth titles start coming out in January, so that's a good place to start. The titles shipping twice monthly will be easier to trade-wait or catch up if you don't want to get too many individual issues. The fifth and final trade for Grayson is released next week.