Interesting

It's likely nucleation. Basically, the water wants to boil, however it can quite get over the hump to produce a gas bubble. When you add salt, the surface acts as a nucleation point. Once the bubble forms, it grows rapidly, often splitting and forming more.

You see this effect at the other end too. Supercooled water will remain liquid, until something becomes available to crystallise around. When this happens, the whole lot will freeze in seconds.

The salt can help "seed" the boiling, by providing nucleation sites for the bubbles to form. So, you end up with more bubbles, but they are smaller. Of course, this effect is only applicable before the salt finishes dissolving, so you're only going to notice it if you throw salt in when the water is already boiling or close to it. Chemists will use boiling-chips (little rocks that don't dissolve) for a similar reason to ensure a smoother boil (smaller bubbles means less splatter, assuming you put them in at the beginning... you definitely don't want to add boiling chips after things are already hot or you're gonna end up with even more splatter than doing nothing).

There are certainly energetic effects caused by the dissolution of salt crystals, but unless you're starting with deionized water or using a crazy amount of salt, the effect is gonna be pretty negligible.

It's just adding a bunch of extra surface area so the bubbles form on it. Like mentos and coke. https://youtu.be/QW7r2RHt6tY

A small amount of salt has a nearly negligible effect on boiling temp. Salting pasta water is for flavor.