Probably the most asked question on any Mac forum. If you're really curious, search for it here. You can find a whole day's worth of reading just the threads on this topic.
I don't run AV Software on my Macs. But I'm not the type of person that gets viruses either. I do run AdGuard now http://adguard.com/ because I can't stand ads. On my Windows machines I run Eset - https://www.eset.com/us/ - again Windows only.
Malwarebytes is great on the Mac. I scan with that every few months or so.