Framing lumber, also known as structural lumber, is the grade of wood used for house framing. For example, studs, headers, roof trusses and floor joists. Wood as a framing material is advantageous as it doesn't undergo much transformation during processing; it has a low embodied energy, it's a renewable resource, and it stores carbon.
One of the primary families of framing lumber is light structural lumber, which is mainly used in residential construction. Light structural lumber is milled from softwood trees like spruce, fir, and pine that are sawn and machine-planed to standard dimensions (2x4", 2x6", 2x8", etc.)