Webserver sessions.
Sessions are IDs that address a timeboxed set of activity performed by a specific client. They are often associated with session storage which records specific details about client-server interactions. In webservers, sessions are often set as cookies in the client which are carried on each interaction with the server, but any method of trading session tokens can work. Sessions are often additionally defined by level of identity verification of the client, with each level having unique IDs and potentially different timeboxes.