Serverside rendering: HTML is rendered on the server and sen to the client to display.
Clientside rendering: data is sent to the client, which uses JavaScript to render templates clientside using that data as input, to output HTML for display (or for mutating the DOM directly).
Clientside rendering: data is sent to the client, which uses JavaScript to render templates clientside using that data as input, to output HTML for display (or for mutating the DOM directly).
That's the essential difference.