Sessions, Opening multiple editors spawns additional sessions. What is the reasoning behind this? (4261633)

Our DBA will only allow a certain number of connections to the Oracle database.

In Toad Data Point, with no connections opened, no sessions are open.
One connection opened, one session is opened.
If that connection opens an editor, another session is opened.
It seems that one can close down all editors with only the connection open, and yet one cannot get back to only one session.
The lowest amount of sessions is two after launching an editor.
If subsequent editors are again launched, the numbers are incremented again properly.
If multiple editors are closed, the multiple sessions decrement to two open sessions.

Why are multiple sessions spawned and what’s the reasoning behind it?