Windows 10 does come with a resident AV - windows defender. It has improved steadily over the last couple of years and is fine for most basic users. Paid AVs do get you better protection plus a host of extras, protected browsers for secure banking, password managers, auto update of programs etc
Eset, Bitdefender and Norton (Symantec) all come out consistently top for paid AVs in comparison tests. Kaspersky, AVAST, AVG also do well. The free versions of Bitdefender, Avast and AVG use the same antivirus engine as the paid versions but suffer from ‘nag’ screens offering various paid extras. I currently use kaspersky but it has some issues with firefox, so I will likely try Bitdefender when the license expires.