Frame Height allows you to fix the height of your frame. If no 'Height' is selected, by default, the height will automatically adjust to suit the content that is within the frame.
Therefore, you will only require this feature if there is a situation where the height must be fixed. Otherwise, there is no need to fix the height of a frame.
Frame Height is often used on the outer 'Row' where you wish to control the absolute total height of the entire 'Row'. Though you can fix the height of any row that you like.
Imagine that you are creating a series of Rows to appear as a table. You decide that you would like to display 4 rows all of even height, in this case 200px high.
Imagine that the volume of text within each row is slightly different, therefore some Rows would, by default, be higher than others. By setting the Row height to 200px, all rows will be fixed at this height regardless of the volume of text within the layout.
Imagine now, that you have more text than the height of the row can accommodate, the text will naturally overflow to the next row. You have 3 options to control the overflow: