Ethernet is one of the core technology that enables most of our communications and data transfer that we do over the internet possible. Its an inexpensive technology for high performance networking.
When your application (no matter what..can be a web browser, a download client etc etc) initiates a connection to a remote server, the application’s job is to transfer the data/request it wants to send to the network protocol stack.
The job of the protocol stack is to break that data down to smaller chunks and wrap it with required information, to send it through the wire. This information wrapped around the data chunks enables the data to be received by the correct receiver, and reassemble the data chunk in the correct order.