Attributes means characteristics. For instance, in a database or a spreadsheet you can apply attributes to each field or cell to customize your document. As a general attribute, you can choose whether it is to be a text field or a numeric field or perhaps a computed field, whose value the application calculates for you.
Then you can apply more specific attributes to the field or cell, such as making the text bold and right-aligned and perhaps in a particular typeface. If a field is numeric, you will have other attribute options available, such as how many decimal places to display, whether to use a dollar sign or a percent symbol, or whether to start a formula in the cell.