When Ctrl+E to highlight formula cells, #REF!, #NAME?, #NUM!, #ERROR! will show for bad formula cells

#REF! ? No reference cell, column

#NAME? ? Function name or named range not exist. Could be typo in function name, etc.

#NUM! ? not a number

#VALUE?

#ERROR! ? Other errors e.g. wrong number of arguments,mismatched ( and ), wrong operator, not supported calculation, etc. e.g. type =A1 A2 not support.