My Windows 10 seems to be running both Norton 360 and Windows Defender

My Windows 10 seems to be running both Norton 360 and Windows Defender. Just noticed the "Virus Protection" pop-up in the lower-right of my screen today. Checked status of Windows Defender and it shows active for 100+ days. News to me. I've kept my Norton 360 up to date for years. Previous threads here don't seem to address this occurrence.