Can you explain what the term SNI means in the context of TLS and HTTPS?

SNI (Server Name Indication) is an extension of the TLS protocol that allows a client to specify the hostname it wants to connect to during the establishment of a secure connection (HTTPS). This is important when multiple sites with different certificates are hosted on a single IP address.

Without SNI, the server does not know which certificate to present to the client, and therefore cannot correctly serve multiple domains on a single IP via HTTPS. With SNI, the server receives the hostname at the beginning of the TLS handshake and selects the appropriate certificate.

Example: if a server hosts example.com and example.org, SNI allows the client to specify which site it is accessing so that the server can send the correct certificate.