I have an imac 24 inch 2021, can I connect a mac mini to it? If so, how does that work?

See the following link:

Use your iMac as a display with target display mode - Apple Supportisplay mode - Apple Support

Your M1 iMac is a computer, not a display for other devices, and you should acquire a separate display for your mini. There is no support for the discontinued target display mode on your M1 iMac.

The ONLY way is via Screen Sharing.

No iMac manufactured since the late 2014 model supports target display mode.

No Mac manufactured staring in 2020 can connect to an iMac in target display mode.