Ozone is the bonding of three oxygen atoms to make O3. This molecule is quite unstable and reacts with other particles in the air.
It is used in air purifiers as a means to eliminate odeour and other stubborn smells like cigarette smoke. The ozone generator releases O3 molecules which react with the bad smelling particles to neutralise them. There’s evidence that it also helps to kill bacteria and airborne viruses.
An ozone generator does not purify the air, it does not filter the air and it does not make the air better to breathe. It simply removes bad smells from the room.