Transformers step up or step down the voltage. Like the one behind my shop has three phase 14.4KVA comming into it. Obviously not useable by standard electrical/electronic equipment. The transformer steps it down to something that can be used. (240 VAC in my case. Two legs of 120.)

The insulators are what the wire is connected to at the pole/tower. Look to the large transmission lines that seem to suspend the wire below each "arm". The sticks of "bubbles" looking thing it is attached to is the insulator. The higher the voltage, the farther the wire must be away from a path to ground or another phase.

Guy I know works helo high line repair. I asked him what happens if he get too close to a path to ground while energized (would it hurt?). He said not at all. His body would just vaporize.

Oh yeah.. The bird or squirrel has no path to ground or another phase to be electrocuted. Should you see dead wildlife at the base of a pole, you shouldn't touch it or the pole. There is a good chance the pole is energized, and is also going to get you if you get close even.