The one closest to the engine is "Bank 1 - Sensor 1"
Bank 1 is always the side of the engine with cylinder #1. Bank 2 is always the side of the engine with cylinder #2. This only matters on the V6, not on the inline 4 cyl. Bank 1 is the bank of cylinders on the firewall side. Bank 2 is the bank of cylinders on the radiator side.
Sensor 1 is the O2 sensor before the cat. Sensor 2 is the O2 sensor after the cat.