SERVER TYPE : DEDICATED

The session is established through dedicated connection.

SERVER TYPE : SHARED

The session is established through shared connection.

SERVER TYPE : PSEUDO
the session that issues the ALTER SYSTEM statement to terminate a session waits up to 60 seconds for the session to be terminated; if the operation that cannot be interrupted continues past one minute, the issuer of the ALTER SYSTEM statement receives a message indicating that the session has been "marked" to be terminated. A session marked to be terminated is indicated in V$SESSION with a status of "KILLED" .and a server that is something other than "PSEUDO."

SERVER TYPE : NONE
session is an idle shared server sesssion.