When a client accesses a website, it communicates with the server through the HTTP protocol. Initially text-based, this protocol became binary with HTTP/2, but its operation is still based on TCP.
Each exchange begins with the creation of a connection between the client and the server. With HTTP/1.0, this connection was closed after each request. But with HTTP/1.1, the Keep-Alive mode became the norm, allowing the connection to be kept open for several successive exchanges.