Spread-Sheets is an application on the computer that shows lots of cells that makes up the whole grid. You can fill them with words or numbers, its up to you. You can use formulas get answers more easily. It also has the ability to re-calculate the whole sheet automatically even if you make a small change in any of the cells.
This application can only work with the info that you have typed in. Only then can you write formulas and tables or graphs. Microsoft named the spreadsheet Excel.
These are some basic formulas that are used in Excel
This is the IF formula, = IF (condition; value "if true"; value "otherwise") This just means that If the contents in cell A1 is less than or equal to zero, then it displays "ordering", otherwise (if the contents of cell A1 is greater than zero) it will display "stock".
In Excel you can Format numbers, apply cell borders, create an Excel table, apply cell shading, filter and sort your data, create a formula and chart your data. If you need help with any of these, there is a website that can help you.