Wires are rarely connected directly to an electrical or electronic assembly. There’s almost always a terminal of some sort crimped or soldered to the end of the wire to interface with a pin, post, connector or another terminal.
Wire terminals are produced in a vast array of shapes, sizes and materials. There are rings, hooks, spades, blades, pins and flags. There are quick disconnects and locking terminals. They can be made from brass or copper and given various platings and coatings. They can be supplied as loose parts or daisy-chained on a reel.