Yes, there is. It is called Windows Defender and it is part of Windows 10. In my opinion there is no need for third party AV programs although it is a matter of the users safety behavior. Security is less a software than it is a concept. No software can protect the user from "wild" behavior.
I am using Windows Defender since my change to Windows 10 and never had a problem so far....
Ditto. But a caution. I read countless posts on the web, on the subject of how to turn off Windows 10 updates. Be aware! If you do this, you also turn off the Defender definition updates, which are important.
For most people Windows Defender is perfectly fine, and it's built in and turned on by default. I use Bitdefender on most of my systems, but on the slower ones I just use Defender because it's really lightweight. I would also download the free version of Malwarebytes and run a scan once a week.