Most features that can be sized can accept relative or absolute size units.
Absolute sizes are units like pixels, points, inches, etc.
Sizes in these units are relative to an absolute measurement and cannot be scaled. This allows the text to change size and the page layout to flow without creating extra whitespace or running off the edge of the screen or paper. Tables and table cells, columns, etc. A fixed-size table cell also cannot expand if its contents expand, for instance because the user has increased the font size. All other values are fixed in size.