A session is basically another SAP instance on your screen. Multiple sessions allow you to work on more than one task at a time. This can save you time and reduces the need to jump from screen to screen.
You can open up to six sessions, and do a different task, or even the same task, in each one. You can move around between the open sessions, and you can close any session without having to log off from the system.
If you try to work on the same record (for example, the material master record for a specific material) at the same time on multiple sessions, you may "lock yourself out" of one of the sessions. If this happens, choose Exit or Back to move out of the transaction. Then you will be able to proceed.
Additional InformationCreating a New Session Creating a New Session and a Task at Once Moving Among Sessions Ending a Session