Why a computer might have more than one MAC Address?

The best way to understand a mac address is like a house.

If you add another networking device then you have another different mac address for it. Maybe like a neighbors house, just the other house is still on your street.

The IP address is like an apartment meaning 1 MAC address and several IP addresses(apartment a, b c and so on).

To have one networking device and more than one mac address would mean that virtual networking has been added and a quick system restore to the point prior to the date the new project started will return all configurations to normal, except there may be a few adjusments.

A computer might have more than one MAC address, if two or more NIC are installed, for example one wired and one wireless Ethernet card.