Just like any other kind of annotation, AutoCAD LT tables have styles. Each style really just has one setting: the table direction (down or up). The real meat of the table style is in the cell styles.
Each table style, by default, comes populated with 3 cell styles: Title, Header, and Data. You can see an example of where each style might be used in the image above.
On the General tab are cell formatting options like Fill Color, Alignment, Format (text, percentage, data, etc.), Type (label or data), and Margins. You can also choose whether to merge new cells into the existing one when you create a new row or column -- this option is useful for Title cell styles.
The last tab enables you to control the borders for each cell of that type -- lineweight, linetype, color, and you can even choose a double-line border. With the buttons at the bottom, you can choose which sides of the cell to apply the formatting to.
For some tables, three styles may be enough. If they're not, though, it's easy enough to create more. The two buttons next to the cell style pull-down enable you to create new styles or modify the existing list. There isn't a separate dialog to manage cell styles -- once you create a new style, you adjust its properties in the Table Style dialog. Cell styles don't translate between Table styles, either. They can only be used in the Table style where they were defined.
Of course, you can always directly modify the properties of existing table cells through the Table Cell contextual tab or the right-click menu. But sometimes it's nice to have styles predefined, to cut down on repetitive work later.