I could write a whole post on wood species as each species has unique characteristics and traits. But, one of the most common types of wood used in DIY projects and furniture building is pine wood (a softwood). Pine is an affordable and readily available option at your local home improvement store and it comes in many sizes. I highly recommend using pine for beginner woodworking projects. Then, as you improve your skill, try working with some different wood species!
With two varieties, red and white, oak is known to be easy to work with and relatively strong. However, furniture makers often opt for white oak over red oak for its attractive figure and moisture-resistance. Depending on the kind needed, oak can probably be found at a local home center or a lumberyard for a bit pricier than other hardwoods.
Typically furniture such as tables and chairs is made using solid stock from hardwoods due to its strength and resistance to warping. Additionally, they also have a greater variety of grain patterns and color and take a finish better which allows the woodworker to exercise a great deal of artistic liberty. Hardwoods can be cut more cleanly and leave less residue on sawblades and other woodworking tools. Cabinet/fixture makers employ the use of plywood and other man made panel products. Some furniture, such as the Windsor chair involve green woodworking, shaping with wood while it contains its natural moisture prior to drying.