This sheet includes QTY (EA), Length (LF), Dim (IN), Extension (BF) and description at the extreme left. Dimensional lumber is a jargon that used for lumber (timber) that is cut pieces to standardized width and depth specified in inches.
Carpenters and timber workers are widely use dimensional lumber in framing timber made buildings. This sheet will help them to calculate the estimate. For wall framing by lumber dimension, "stud," or "precut" sizes are easily getable, and usually used in different size.