I take it that you're someone who's just been "thrown" into this job of administrating a database (or just playing with Oracle). Either way, I would advise you to seriously sit down and read up on the basic understandings of Oracle and how it works before you break something. Once you have the basic concepts down (or have your company send you to some classes) then come back here and ask for advise.

When you ask what does connected to an idle instance mean, that's like asking what does "P" stand for on the shifter of a car?

P= Pass
R= Race
N= Nitrous
D= Drag