circle with a line is called the "Prohibitory" symbol.
Your Mac appeared to have all the right stuff to start up. But part way through the process, an important fundamental file required was found to be defective or the wrong version for your specific model Mac.
Try to repair the disk.
If no joy, a MacOS re-install in place is likely needed. By design, this does not alter any user files. But it will re-write over 350,000 files, so if your disk is marginal, this may force it over the edge into failure.
If you do not have a recent backup, it would be more prudent to buy an external drive, and do a new Install on the external drive, preserving your old internal drive for later attempts to salvage.