4.4 Function and Chart
You can type in a formula (though you have to be sure it's exactly right) or you can use Excel's preset formulas called functions. If you type in the formula, you must start with an equal sign, so Excel knows that the data in the cell is a formula.
A chart is a visual representation of your data. By using elements such as columns (in a column chart) or lines (in a line chart), a chart displays series of numeric data in a graphical format.