The Grid section draws a table of lines inside the element - rows, columns and a frame round them. On its own it's a ruled box, for a form or a price list; with the text's Text mode set to Grid, the text fills its cells.

The grid appears once its Line size is above 0: that's the thickness of its lines, in points. Until then the section shows only that box.

The grid
Line style, Dash end style, Composition, Sketched style, Antialias	How the lines are drawn - solid, dashed or dotted, single or double, straight or hand-drawn. See Borders, which use the same styles.
Frame	The line round the outside. Switch it off to have only the lines between the cells.
Text padding	How far a text in the cells keeps from their lines.
Rows, Columns	How many, from 1 to 100.
Row size mode, Column size mode	Proportional sizes: all the same, sharing the element's size. Fixed size: all the same, at the Row height or Column width you give. Custom sizes: one size each - see below.
Pen	The color of the lines.
Padding	Space between the edge of the element and the grid. See Padding.

Custom sizes. With Custom sizes, you get a box for each row, or each column: Row 1, Row 2 and so on. You give every one but the last; the last gets what's left, and its box shows how much that is. The sizes are real lengths: they stay the same when you resize the element.

If the sizes add up to more than the element, the rows or columns that don't fit simply aren't drawn - and they come back when you make the element bigger. Fewer rows and then more again gives you back the sizes you had.