The NEMA 10-30 has two Hot and one Neutral.
The NEMA _6-30 has two Hot and one Ground.
The NEMA 14-50 has two Hot, one Neutral, and one Ground.
The Ground and the Neutral are connected together inside your electrical panel
so they have the same potential, but they don't serve the same purpose.
The Neutral can bring back current to the transformer if only one phase is need,
some accessories, like a timer, a fan, or a light inside a stove range might only use one phase.
While the ground protect in case a Hot wire touch a metal part of a device.
New plugs should have a ground, or even be GFCI (ground-fault circuit interrupter).
Basically the difference between Neutral and Ground is that the Ground provides a better protection against choc.
- If one accessory uses only one phase, so some current will go through the Neutral,
creating a difference of potential along the Neutral between the front Panel and the plug.
- In this situation, if a person touches the Neutral and the Ground (the wire or the ground soil)
at the same time, the current might goes directly from Neutral to the Ground if there is less resistivity,
using the person body thus creating a choc.
Note: This is not a scientific explanation, just some layman narratives.
The Tesla charger don't use the Neutral, but there is a test for Ground or Neutral.
Some people using a portable generator were not able to use a Tesla charger for that reason.
But there a workaround explained in some other threads.
Note: You might consider getting a ToU (Time of Use) from your local electrical company to get a discount rate at night.