Despite their names, hardwoods and softwoods do not necessarily differ by their hardness, but instead their names imply a taxonomic division between species.
It may be easier to think of hardwood trees like oaks, maples, and birches as broadleaf deciduous trees (they are not evergreen trees). Also, these trees are considered to be angiosperms, meaning that they produce seeds from pollinated flowers. Conversely, softwood trees like pines, spruces, and firs are conifers, meaning they are evergreen and they have scale-like foliage or "needles". Generally, when it comes to furniture, hardwoods are the better choice because of the variety of species and their characteristics are typically more suitable for furniture. Softwoods can be used for furniture however, should you desire that specific look and feel.
They are gymnosperms, meaning that they reproduce through their cones instead of flowers. They are made up of tracheids, a type of cell that comprises about 90 to 95 percent of coniferous woods. They are fiber-like and much longer than they are wide, making that specific softwood texture, and great for making paper! Depending on how thick in diameter each tracheid is, determines the texture whether it be coarse, medium, or fine.
The nonliving tracheids support the wood's conduction and support. This exchange seems to occur from earlywood to latewood (remember the growth rings?). When looking at the earlywood, you can see the tracheids are larger and thin-walled, which makes conduction efficient. Latewood is the opposite, however, it provides a great amount of support for the tree.
The variation between the earlywood and latewood density can have an effect on the overall evenness of the grain, so it is important to examine it. This can result in an uneven staining, which may be unattractive for your furniture. Also, remember that if you are working with a softwood that is flatsawn, you might not want to use them for flooring as they wear out more quickly, leaving behind raised areas of latewood. Another thing to look for is for resin canals. In softwoods, resin canals which excrete pitch are common, and can cause difficulty in drying and staining.