LDO pass transistor operation region
1) Poles are a property of a control system transfer function, they are the points on a complex plane where the transfer function goes to infinity, and electrical system can be analyzed like this as well. It basically means that the capacitor ESR and capacitance need to be carefully selected for stable operation. Wrongly selected capacitor can lead to unstable operation, it might even oscillate just by itself.

2) It means whatever the ripple amplitude is at regulator input, it will be 60 dB less on the output.That's a factor of 1000 said in a convenient fashion.