Canbus is controlling the power to the radio (allowing it to auto-turn off after 20 mins when ignition off, for example). It will also control the display dimming, making it less bright when the headlights are turned on. It's probably also responsible for the 'speed related volume' function, that automatically raises the volume as you drive faster.
I suspect the standard radio has a permanent 12v live supply (the red wire with green trace near your thumb in your photo), and then the canbus signal operates a relay inside the radio as necessary... the yellow and blue wires show your radio has Canbus connected.
You are likely to need an adaptor connector such as this to interface to a non-Fiat radio...
https://incartec.co.uk/product/Fiat-Alfa-Romeo-CAN-BUS-Radio-ISO-lead . This adds that relay outside of the radio (its the small black box top right of the photo). But, it will be a squeeze to get this in behind the radio in the dash - your existing plug goes into the big black connector bottom left of the photo, and the red and black plugs upper part of the photo go into the new radio to take the connections through.
On models with steering wheel controls (and so a Blue and Me or uConnect radio), there is a second plug that connects the radio in the dash to a control unit elsewhere in the car: this is the other connector shown in the wiring diagram on the back of your radio. You'll see there 'phone', 'mute' etc on the labelling of those pins.
Also, (as covered in anther thread), note that although your current radio has cables connected to all the speaker contacts (the ones nearest your fingers in the photo), but that this wiring does not go all the way into the rear doors - the Pop model never did have rear speakers, and now, it seems no Panda does. Bear this in mind if your planned new radio has a front/rear fader.
