Solar radio bursts are brief periods during which the Sun's radio emission is elevated above the background level. They are signatures of the same processes that lead to the more widely-known forms of solar activity such as sunspots, solar flares, and coronal mass ejections. Radio bursts can exceed the background radiation level only slightly or by several orders of magnitude (e.g. by 10 to 10,000 times) depending on a variety of factors that include the amount of energy released, the plasma parameters of the source region, the viewing geometry, and the mediums through which the radiation propagated before being observed. Most types of solar radio bursts are produced by the plasma emission mechanism operating in different contexts, although some are caused by (gyro)synchrotron and/or electron-cyclotron maser emission.