Brushes come in a wide range of shapes and with several different bristle materials and types. Traditional brushes have close-set bristles made of nylon, plastic or wild boar hair. Natural boar bristles are softer and more pliable, so they're gentler on your hair and scalp, and don't usually cause breakage or other damage. They also help distribute the hair's natural oils, create healthy shine and reduce static. (Tip: If you have lots of static electricity in your hair, spritz your brush with a little hair spray and brush from the roots to the ends to tame flyaways.)
Brushes with fat, widely spaced bristles are also available, usually with plastic, flexible metal or wooden bristles; make sure the bristles have rounded tips so you don't scratch your scalp. Some brushes have bristles attached directly to a plastic or wooden handle; others have bristles set into a rubber or plastic cushion or a metal cylinder.
Flat brushes have an oval or rectangular back and bristles set in a slight curve. They are used for minor styling jobs and for brushing out tangles and styles.
Paddle brushes are wide and flat. These are good for long hair and for smoothing straight or slightly wavy hair in the final stage of blow-drying.
Round brushes have 360-degree bristles and are used during the final stage of blow-drying. They come in a variety of diameters -- the smaller the diameter, the tighter the curl. Narrow round brushes with metal cores are especially effective for creating curls; as the metal heats, the brush also acts as a sort of curling iron. Wide round brushes are good for straightening and smoothing hair. Be careful when you use a round brush: Don't wind your hair too tightly, or it might become badly tangled.
Half-round brushes are an all-purpose staple: They can be used like round brushes for creating a style, or for just brushing your hair out.
Vent brushes have wide-set bristles and holes, or vents, in the base. This type is commonly used for blow-drying: The openings allow air from the dryer to circulate freely, reducing drying time and creating more volume.