Relative reference in Excel is a type of cell reference that is relative to the location of the cell. By default, all cell references in Excel are relative references. When a formula with a relative cell reference is copied to another cell, the reference changes based on the relative position of rows and columns. For example, if you copy the formula =A1+B1 from row 1 to row 2, the formula will become =A2+B2.

On the other hand, absolute reference in Excel is a type of cell reference that remains constant no matter where it is copied. An absolute reference is designated in a formula by the addition of a dollar sign ($) before the column and row. For example, if you use an absolute reference like this in cell E2: =$C$2, it will always refer to cell C2, no matter where you drag or copy and paste that formula.

Mixed reference is a combination of relative and absolute references. It is used less frequently than relative and absolute references. A mixed reference can precede either the column or the row value with a dollar sign ($), which fixes either the column or the row.

To switch between relative, absolute, and mixed references in Excel, you can select the cell that contains the formula, select the reference that you want to change in the formula bar, and press F4 to switch between the reference types.