ONT (Optical Network Terminal) is a device that is used in fiber optic networks to convert the optical signal into a form that can be used by the customer's devices, such as a phone, computer, or TV. It is typically installed in the customer's premises.

Ethernet, on the other hand, is a commonly used networking technology that allows devices to communicate with each other over a local area network (LAN). It uses a set of protocols and standards to define how data is transmitted and received over the network.

In summary, ONT is a device used in fiber optic networks to interface with customer devices, while Ethernet is a networking technology used for communication between devices on a local network.