Cellpadding is a syntax and command for certain kinds of programming that increases the white space in table designs.
Techopedia explains Cellpadding
One of the most common uses of cellpadding is in Web design. Earlier versions of HTML included cellpadding commands that allowed designers to render a table with more white space in each individual cell of the table. The boxes would get larger, but the text would stay the same size, producing a kind of greater margin in each box. Now, the W3C is alerting users that HTML5 does not have cellpadding and that this command should instead be done in Cascading Style Sheets (CSS), a new language protocol that has emerged to augment HTML in Web design.
Other kinds of technologies have alternative solutions for creating cellpadding. For example, in Microsoft Excel, users can increase cellpadding in the spreadsheet by increasing the size of columns and rows, and then using a "center" command.