Final answer:
An absolute reference is a fixed cell reference in spreadsheets that does not change when formulas are moved or copied. It is marked with a dollar sign before the column letter and row number, such as $A$1.
Step-by-step explanation:
A absolute reference is a permanent reference to a cell in spreadsheets such as Microsoft Excel or Sheets and does not change when the formula is copied or moved to another cell. This type of cell reference is prefixed with a dollar sign ('$'), for example, $A$1. It always refers to a cell in a fixed location. When formulas are copied across cells, absolute references do not adjust to the new location, unlike relative references which change based on the relative position of rows and columns.