K2 means Vitamin K-2. It is sold in two kinds: Vit K-2-MK4 and Vitamin K-2-MK 7. I buy the Vitamin K-2-MK7 one to take with the Vitamin D3. It enables the vitamin D to be deposited in the proper place (instead of the joints).
Yeah, the K2 helps with increased vitamin D levels, higher D levels then just D alone.
-SB