Can someone help me understand what role the MAC address plays in the OSI and TCP/IP models?

I'm studying for my CCNA (just started my first quarter, Introduction to Networking), and I'm learning about the OSI and TCP/IP model. I am understanding most of the layers from each of the models, however, one thing that has started to really confuse me now is the addition of MAC addresses and/within the Data Link layer.

Can someone help me understand the significance of the MAC address and what role it plays, along with the Data Link layer. I know the MAC address comes in to play at the Data Link layer and that it is used for computers on the same local area network, but other than that I'm having a hard time understanding/wrapping my head around it. For the most part, I get the rest of the layers in each of the models.