#2
Check the back of your bass, if you have a battery compartment, it's active. It's a small preamp which boosts the signal from the bass.
The Inputs are made to deal with the different signal strengths, whereas the active signal should be stronger and passive the weaker. This means that the active input lowers the signal strength a set number of dBs to even out the level.
Maruszczyk Jake X Redburst
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Ashdown MAG300H + Ashdown 1x15 (Eminence Delta 15)

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#3
If you have batteries, or in some uncommon cases, a power cable going to the back of your guitar (not the input jack), then they are active. Active pickups basically make the signal stronger, and to some ears, better.

I don't like actives, they sound nice, but are WAY too much trouble for me.

EDIT: didn't read the question right. If you have active pickups, I'd assume you plug into the active jack. Or Passive into passive.
#4
Your Squier is more than likely passive. An active input just cuts the signal to the preamp by about 10dB to even out the volume level and prevent preamp clipping. Usually active basses have an active preamp which allows for tone shaping on the bass itself. Sometimes they have active pickups which are just hotter, but it isn't as common.