A cinder cone is a steep conical hill formed above a vent.  Cinder cones are among the most common volcanic landforms found in the world.  They aren't famous as their eruptions usually don't cause any loss of life.  Cinder cones are chiefly formed by Strombolian eruptions.  The cones usually grow up in groups and they often occur on the flanks of strato volcanoes and shield volcanoes.

Cinder cones are built from lava fragments called cinders.  The lava fragments are ejected from a single vent and accumulate around the vent when they fall back to earth.

Cinder cones grow rapidly and soon approach their maximum size.  They rarely exceed 250m in height and 500m in diameter.

Cinder Cone.

The shape of a cinder cone can be modified during its (short) life.  When the position of the vent alters, aligned, twin or secant cones develop.  Nested,buried or breached cones are formed when the power of the eruption varies.

A great example of a cinder cone is Paricutín in Mexico.  It was born in February 20, 1943 in a corn field and grew to 300 feet in 5 days.

Information supplied by: http://volcano.und.nodak.edu