What does it mean if SERVER = 'NONE' in v$session?

Definition:
SERVER  VARCHAR2(9)  Server type (DEDICATED| SHARED| PSEUDO| NONE)

From metalink:
In MTS/Shared Server configuration when you see value 'NONE' (as shown below), it means there is no task being processed by shared server for that session. The server column will infact show status of 'SHARED' if there is some task being processed at that particular time by the shared server process for that session.

In is also proved by the fact, that STATUS of session is always 'ACTIVE' for the sessions with 'SHARED' as value of SERVER and 'INACTIVE' for those with SERVER='NONE'.