A circular reference in Excel occurs when a formula refers to the cell containing the formula itself, either directly or indirectly. This creates an endless loop that can potentially crash your workbook and prevent the formula from outputting a result. Circular references can be unintended mistakes or intended iterative calculations made by experienced Excel users. There are different ways that circular references can arise in Excel spreadsheets, such as using iterative calculations, linking two or more formulas in a circular reference, or incorrect use of the CONCATENATE function.

To find and remove circular references in Excel, you can follow these steps:

1. Review the formula in the cell that Excel identifies as having a circular reference.
2. If you cant determine whether the cell is the cause of the circular reference, select the next cell in the Circular References submenu.
3. Continue to review and correct the circular references in the workbook by repeating steps 1 through 3 until the status bar no longer displays "Circular References."
4. You can also use the Trace Precedents or Trace Dependents feature to move between cells in a circular reference and show the tracer arrow.
5. If you want to allow circular references, you can enable iterative calculations in Excel. This allows formulas to iterate and repeat until a specific numeric condition is met.

Its important to note that circular references can be troublesome and should be avoided whenever possible, as they can lead to performance issues and other problems that are not immediately apparent.