In the world of IT and computer science, the word "session" is a reference to a certain time frame for communication between two devices, two systems or two parts of a system.

In some cases, a session is user-initiated. For example, the time frame for an interaction between two personal computers used in online chatting or messaging is considered a session. The individual users initiate it, and end it when it is finished. Other kinds of sessions are initiated by technology. One of the most common is a client/server session between a server and a personal computer or other device or system accessing that server. Software Developers and others have developed session protocols for handling these interactions between systems. These cover all of the many interactions required for browsing the Internet, as well as sending and receiving email through various email clients. It is interesting to note that many of these sessions are actively hidden from the end users; in other words, the common user does not recognize that these sessions are occurring, and does not know much about what happens during these sessions. Analysis of technology-initiated sessions is largely the province of network administrators, security experts and others with a close knowledge of an interactive network.