Plasma science can seem complicated. I'll try to make it as simple and quick as possible. Plasma cutters heat the gas enough to melt it. After the metal has been heated enough to melt, it can be blown with gas to make a cut. There is much more to this process, but that's for another day. (Or, you can conduct your own research, if desired).
Fiber laser machines have a higher efficiency rate at cutting thin materials than traditional cutting machines. A fiber laser machine has the ability to cut thin metals as small as 25mm. The fiber lasers will start cutting metal less effectively after that point. To cut ticker materials above 25mm (or 1 inch), you'd need high levels of power.
Fiber Laser Marker Machine