What does 255.255 0.0 mean?

Excuse me, I'm a bit confused about a technical aspect related to networking. Could you please clarify what the notation "255.255.0.0" represents? I've heard it mentioned in discussions about IP addressing and subnetting, but I'm not entirely sure what its specific function or purpose is. I understand it has to do with the division of IP addresses into subnets, but I'm seeking a more in-depth explanation. Could you elaborate on its significance and how it's used in the context of network administration and security?