#ERROR! is a common message encountered in spreadsheet applications like Microsoft Excel or Google Sheets, indicating that a formula or function has encountered an issue. This error can arise from various reasons, such as referencing invalid cells, using incorrect syntax, or performing operations that are not mathematically valid. To resolve #ERROR!, users should carefully check their formulas for typos, ensure all referenced cells contain valid data, and verify that the operations being performed are appropriate for the data types involved. Understanding the source of the error is key to troubleshooting and correcting it effectively.