Although it sounds like some procedure that a celebrity would have done in a secretive Beverly Hills clinic, when it comes to wiring, a "butt splice" is a fairly common connection used in electrical work that falls under the category of crimp connectors.
It's used to either terminate a wire that comes to an exposed end or to join two more more wires together. To use, slip the end of the wire or wires into the crimp until they're overlapping, then squeeze with pliers to close the crimp.
BuyHeatShrink's high temperature butt splices add an extra level of security to the mix with a layer of 2:1 heat-shrink tubing around the crimp that has an adhesive in the middle. When shrunk, the crump section is secured and the adhesive melts and hardens to create a water-proof seal.
Butt Splice is an irradiated, thermally stabilized heat shrinkable, dual-wall sleeving that comes in crimp splices for 26-8 AWG wire, Nyax Wire Terminal for capping open wires, and a butt connector version of the latter, Nyax Wire Connector.
A: Yes. The only difference is the crimp connector inside, into which you need to insert the terminal end of one wire or the join ends of two or more wires before crimping them together.
After that, it works just like regular heat-shrink tubing, using a heat gun or other source to shrink to one-half its original diameter and melting the adhesive inside for a nearly permanent, seal resistant to water, spray, oil, saltwater and most hazardous chemicals.
A: You could, but it would be nowhere near as safe or secure. The metal crimp inside the butt splice helps to keep the wires together securely, plus it's conductive, so will guarantee a good connection.
Butt splices are also rated for conductivity, like fuses or circuit breakers, so you can be confident in how much current you can run through them without blowing out the connection or melting the connection.