What is meant by cell reference, absolute cell reference and relative cell reference?

Cell reference : It identifies the location of a cell or group of cells in the spread sheet also referred as a cell address. Absolute cell : reference means a cell which consists of the column letter and row number surrounded by $ sign e.g. $ D$6. It is used when we want a cell reference to stay fixed on specific cell. Relative cell reference : means that as a formula or function is copied and pasted to other cells, the cell reference in the formula or function change to reflect the new location