There are two types of cell reference; absolute and relative. When moving or copying cells it is important to know the difference between these two types, when and how to use them.
What are relative references?
With relative cell references, cell addresses are altered as you move/copy the formula.
C2 contains the formula A2+B2 ie it adds the values in cells A2 and B2 (the cell to the left and two to the left).
When this formula is copied to the next row the formula automatically changes to add the values in the box to the left and two to the left of C3 (ie A3+B3).
Results of this formula: 15, 22, 49.
What are absolute references?
This uses the exact address of a cell. When copying a formula this cell reference will not alter. Use the dollar sign ($) to indicate absolute references.
The formula in C2 adds the figures in A2 and B2. However the cell reference B2 is now indicated as an absolute reference through the use of the dollar sign. When this formula is copied down the value of the first cell reference changes (A2, A3 etc) however the second cell reference remains constant (B2).