• The user starts a tool (SQL*Plus, Oracle Forms, ...) as a user process
  --> a server process is created on the Oracle Server
  --> the server process communicates with the instance on behalf of the user process
• Connection = communication pathway between a user process and the Oracle server through :
  a local connection (local access tool --> local Oracle server)
  or
  a client-server connection (local access tool --> network --> remote Oracle server)
  or
  a three-tiered connection (local access tool ie browser --> network --> remote Application server --> network --> remote Oracle server)
• Session = specific connection from a client to the server (login/logout)