system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is the difference between Watts (W) and Volt Ampere (VA)?

It seems to play a role wether the system is DC or AC, but I cannot get my head around this.
gpt
VA is used in AC circuits because those circuits have real power and reactive power.

The easy thing is what's called real power which is the energy you want transformed into something else: light, heat, a motor spinning, etc. It's measured in watts. There's also reactive power which is the energy used to create the fluctuating magnetic and electric field that allow AC machines to work. Those fields require current to flow as they build up and collapse, but you get the energy back so they don't consume real power. Reactive power is measured in volt-amps reactive, or VAR.

Real and reactive power combined give you the circuit's volt-amps. Mathematically, real and reactive power are at right angles so we just use (watts)^(2) \+ (VAR)^(2) = (VA)^(2) . You may also see the term power factor. That's real power divided by total valt-amps.

Knowing how much VA a circuit needs is important because all the part it's made of need to be able to handle that current and it's more than just the current that's making power.

EDIT: Stupid autocorrect. Changed "mother" to the "motor" it should have been.