Can anybody help me and tell me what this wire is for

 

Definetly not oem stuff. Some aftermarket stuff that has stolen power from that fuse feed. Atleast it has fuse on it. Unless that fusebox has blown pcb and that is the feed wire for the device that fuse used to feed.

 

Not sure should I hook it up to the positive

 

It sure looks like normal spade? connector that has not been crimped correctly and wire just have come out. Just crimp another one and replace old one.

 

Just power for some aftermarket accessory a PO has used and removed. Follow the cable if you are especially curious to know or tidy up/remove if you're not.

Graham