The server serves the whole document then disconnects the client, aka end the TCP connection. Also, the server does not store any information about the request after disconnection.
In the simplest form HTTP connections are established between a user agent and a server, but there can be more complicated situations also.
Some server sitting between client and server which can modify requests.
It acts like a receiving agent that acts as a layer above servers, for example, AWS API gateway.
A tunnel acts as a relay point between two connections without changing the messages
Client ---> Tunnel A ---> Tunnel B ---> Tunnel C ---> Target server
Although HTTP uses TCP as the underlying protocol, it can use other protocols as well such as UDP.