I have been using black electrical tape since I was a kid.
My Dad was a DIY of considerable skill, and I used to play in the basement and be his helper, he always had several rolls of tape so it became one of my toys.
Black tape has many uses, and has certain properties that make it a versatile tool.
Insulation:
The main use of black electrical tape is to cover bare electrical wires. If applied correctly, the tape will last for many years. If applied incorrectly, it will start to separate and get sticky in short order. Each wrap is good for 200-600V depending on the thickness, so a carefully taped wire can have better insulation than the wires on either side.
The tape is designed to be pliable and stretch so it can conform to irregular surfaces. The trick to making a tight long lasting covering with tape is in when and how much you stretch it.
Temperature extremes will make black tape stretch and contract, loosening the adhesion in the layers. To prevent this, when making the final wrap, always do it with nearly zero tension in the tape, to prevent the end from shrinking back when heated. A final and powerful way to make the taped joint stay together, is to use PVC pipe cement to coat the outer layer of tape and glue it together. The cement sets up in a few minutes, and will protect the tape for many years even outdoors in the weather, and the joint is waterproof.

The inner wraps need to be fairly tight so air is not trapped in side.
The quality of black tape is a measure of how much stretch can be put into the tape before it breaks. Never stretch to more than 70% of the breaking point, as breaking point and pliability drop when the tape joint gets cold, and the tape could crack through all layers.