There are different ways to measure the effectiveness of electronic air cleaners, one way is with a minimum efficiency reporting value (MERV) rating. This measures how effective the air cleaner is at removing airborne particles from the air. Whole home electronic air cleaners installed by an HVAC contractor use a process to charge airborne particles, and then collect those particles as they accumulate on an oppositely charged “collector”. The particles are then destroyed (molds, viruses, etc). This is described as a 3-step process.

A drawback to some electronic air cleaners, is that they can create ozone which isn’t healthy. Not all of them do, in fact some such as the Lennox PureAir™ Air Purification system actually destroy ozone. See the article from the EPA about ozone and air cleaners: Ozone Generators. The EPA also has a PDF with comments on air cleaners in general, which might prove helpful as you begin researching what is right for your home.