Spreadsheets are made up of rows and columns, which form a table or grid. A cell is a specific location within a spreadsheet and is defined by the intersection of a row and column. Since most spreadsheets use numbers to define rows and letters to define columns, cells are often referenced by a letter and number combination.
For example, the cell A3 is located in the first column (A), in the third row of a spreadsheet. The cell B3 would be immediately to the right of A3 and the cell A4 would be directly below it. These examples are relative cell references, since they are based on the actual names of the cells. If a user changed the name of column A to "Income" and the name of row 3 to "Q3," the reference would be "IncomeQ3" instead of A3. However, you could also refer to the cell by the absolute cell reference, which is defined by $A$3. Many spreadsheet programs support absolute cell references, which are useful when creating formulas.
Cells may contain several data types, including numbers, dates, times, currencies, percentages, text, and other types of data. Most spreadsheet programs allow you to format cells for different data types, which helps ensure uniform entries across multiple cells. For example, you could format the active cell (or currently selected cell) to US dollar currency. If you enter "123" in the cell, it may automatically change to "$123.00" when you press Tab or Enter or click outside the cell. If the active cell is formatted for a date, the text "1/2/3" may change to "01/02/2003."
Cells may contain manually entered data or the results of calculations from other cells. For example, cell A20 may contain a formula that produces the result of the summation of cells A1-A15. Cell C5 may contain a formula that averages all the numbers in the B column. The data in spreadsheet cells that contain formulas are dynamically updated when the data in referenced cells are changed.