If you are using Windows 10, it comes with a free pre-installed anti-virus called Windows Defender. In my humble opinion, this is all the AV that you need. This is based on my many years of evaluating AVs, and on independent websites that test AVs.

You should always install antivirus if you use your computer online. Any will work including what is included in Windows 10. What you want to use is really up to you. You will find different opinions on all of them.