My startup disk disappeared with the question mark and I cant reinstall mac
I restarted my iMac because it was really lagging out and I just wanted to reset everything. But once I did, my startup disk disappeared and I got the question mark folder. I went to Recovery mode and it said I had to fix it with Recovery Mode? That kind of confused me so I decided to reinstall Mac, as it wouldn't take to long to download all my applications and more. But I couldn't reinstall mac because there was no disk to install it on. So I'm in the middle of a giant loop and don't know what to do. Can you help me? Thank you!
iMac 21.5″, macOS 11.3