In the context of spaceflight, a satellite is an object that has been intentionally placed into orbit. A few of these satellites are balloon satellites. They are satellites that are inflated with gas after they have been put into orbit. There are also other human-made objects which are also called satellites, only placed in a much lower altitude, and with a very different operating method. These are actually regular high altitude balloon, but providing services traditionally provided by orbiting satellites.
Flat-Earthers deny the existence of satellites, and after they discovered the existence of balloon satellites, they started to use the fact as “proof” that orbiting satellites do not exist. It is the fallacy of hasty generalization. Using the same “logic” they are using, we can use the existence of trucks to “prove” buses don’t exist.