Inverter generators are a relatively recent development, made possible by advanced electronic circuitry and high-tech magnets. These are generally 3-phase generators that output AC current like most traditional generators, but that current is then converted to DC, and then “inverted” back to clean AC power that maintains a single phase, pure sine wave at the required voltage and frequency.
Because these units employ the technologies used by both generators and inverters, they are perhaps most correctly called “inverter generators” but since people tend to simplify terminology, “inverter generator” often gets clipped, sometimes to “inverter” and sometimes to “generator” which leads to confusion as to what is what and which one is being discussed. In spite of this lack of clarity, both terms are commonly used to refer to inverter generators, even by the manufacturers. (As a side note, it should be mentioned that Inverter Generators are also sometimes called "I-Generators")