For me, an inverter is a power electronic device that converts current with a fixed frequency interpreted by the sine function and a specific power, which is taken, for example, from a battery. On the other hand, a power electronic device that has the ability to change the frequency, voltage and load current control is a frequency converter. In my Studies, published, among others, on RU-vid, I present these devices in the presented way. I think that's a pretty accurate description of how they work. Regards!