Brush

Round: The long closely arranged bristles of these brushes make them useful for detail
Flat: These are used for spreading paint quickly and evenly over a surface. They will have longer hairs than their Bright counterpart.
Bright: These are flat brushes with short stiff bristles and can be useful driving paint into the weave of a canvas in thinner paint applications, as well as thicker painting styles like impasto work.
Filbert: Flat brushes with domed ends. They allow good coverage and the ability to perform some detail work.
Fan: These are used for blending broad areas of paint.
Angle: These, like the Filbert, are versatile and can be applied in both general painting application as well as some detail work.
Mop: A larger format brush with a rounded edge for broad soft paint application as well as for getting thinner glazes over existing drying layers of paint without damaging lower layers.
Rigger: Round brushes with longish hairs, traditionally used for painting the rigging in pictures of ships. They are useful for fine lines and are versatile for both oils and watercolors.

The term brush refers to a variety of devices mainly with bristles, wire or other filament of any possible material used mainly for cleaning, grooming hair, painting, deburring and other kinds of surface finishing, but also for many other purposes like (but not limited to) seals, alternative traction systems and any other use imaginable for this tool.