Question marked as
Not sure how you got to this spot, but being that is your startup drive - the house icon indicates it's where your Home folder lives - you will not be able to alter it while running the Mac normally. You will be required to boot in Recovery to reformat that volume... which will erase any data already on the drive; your Home folder and user data.
Before you do anything else, make sure you have created and on hand a Time Machine backup of your computer to an external drive. You may need it soon.
After that, you will need to boot in Recovery again, reformat that drive and Reinstall macOS to fix this issue.
What model and year is your Mac?
What macOS version are you running?
