Where Are Volcanoes Formed?

Volcanoes normally form where two tectonic plates meet, here the weaker plate (either oceanic or continental) gets subducted under the stronger one-normally the continental- this is called the subduction zone. Whilst the one plate is going beneath the other, lave and molten rock as well as more, escapes from the earths core. This forms new land but the new land has a vent/ pipe through which lava and such alike escapes from the earths core. This is called a volcanic eruption. The vent is connected to the earth and has a Reservoir/magma chamber where lava and alike is stored. This whole process is caused by the movement os convection currents beneath the earths crust.
Hope that helped,

A volcano is opening on Earth's surface which allows hot molten rocks, ash and gases to come out. Volcanoes are found on those areas of the earth where divergence and convergence of  tectonic plates take place. E.g. Volcanoes at  Mid-Atlantic Ridge are caused by divergent tectonic plates and  at Pacific Ring of Fire volcanoes are caused by convergent tectonic plates.
Formation of volcanoes can also take place where there is stretching and thinning of the Earth's surface.

The volcano can formed at the land and also in ocean