4 stage HEPA filter with additional (odor control) carbon filter and particle detection that determines fan speed. For smoke, dust, pollen, etc. Whatever's in your air. Also has a "Pre-filter" and an "ionizer" which I have no idea what they are. Magic?
This is the black model - if you Google these purifiers, apparently the standard is white? This is room-size, not whole-house size (up to 361 sq. ft.).
For more detail than I can get you, Wirecutter reviewed this (and liked it)...
https://www.nytimes.com/wirecutter/reviews/best-air-purifier/
... and Coway has a ton of info about it on their website too:
https://cowaymega.com/products/airmega-200m?variant=33436687237255
The filter is in good shape - we just used it this summer while we had an exchange student and had to relocate the kitty litter into Human Living Space. I'm told the HEPA filters last about a year, depending on what kind of things are in your airspace. You can get replacements easily, but they're not precisely cheap (~$50/set).
What we liked:
*It's really quiet when running - I had it next to my work desk and didn't notice it running when it was in "Auto" at low speed (Blue).
*It has an "Eco" mode that will shut the thing off if your air quality is good for 30 minutes - occasionally kicking itself back on to check. So it's not constantly running if you don't want it to.
What to be ready for:
*When it detects that air quality is poor, the fan speed and filtration go into higher speeds - either medium (Purple) or high (Red). Those can be noisy. It's not like an airplane, but it's also not like you'd want to be right next to it trying to have a conversation. Like a fan on high speed - it moves a lot of air fast.
*Ours only kicked into purple/red a few times this summer - first when there was Canadian wildfire smoke for a few days and we had the windows open (probably should have closed them, duh)... second when we burned stuff in the kitchen.
Unit is not tiny but it's lightweight and easy to move around.
Say the word if you have any questions!