system
Given the following post, respond as if you're commenting on Reddit:
human
What's the point of MAC addresses when devices have a private IP address

You can also change both your IP and MAC address, right? It seems like 2 things that have the same purpose.
gpt
You can't change your MAC address, although you can spoof another MAC address. The MAC address is unique to the piece of network hardware.

The real reason for the difference comes down to the function of the layers in the TCP/IP network stack. The MAC address sits at the data link layer, one of the lowest layers of the stack and is the unique address ID of the hardware. That's its role - to ID your computer to other computers. But it doesn't give you any more information than that, such as the location on the network.

The IP address is used at the network layer. It is useful because the formatting of the address and the range of values tells you information about the location on the network of the computer you're looking for. To give a simple case, if the first number of the IP address is 127, you know it is a local address, which limits the space you have to search to find the corresponding machine. Thus, generally speaking, an IP address is relative to the network that it's on. It's true that you can have a static IP address, which is useful for stuff like web servers, but even then the address values mean something.

So IP addresses are useful for network management, but are not normally unique, because the number of possible addresses is not large enough. MAC addresses uniquely identify a computer, but are not flexible to make it easier to find a device. It is similar to the reason computers have both IP addresses and URLs. The URLs make it easier to handle things at a more abstract, human-friendly level, and can be mapped to an IP address for network purposes.

To use a non-computer example, it's like the difference between your house having an address formatted with house number, street name, and city. With that info you can find the house even if you've never been there before. A MAC address would be like assigning your house a random unique number. It's ideal for uniquely identifying the house, but no help at all in finding it.