purpose of small wire on negative cable

[broncobuckinaround]

hahaha i knew that i was just seein if you knew.

 

[GingerKing13]

what is this connector called??? i need a new one as mine i believe got hit by my alternator and chunked up and at that same time the truck bucked and stalled as if i had no gas and for 2 weeks now i dont get a check engine light when i turn the key forward and i dont hear my fuel pump run...