Magma is found in a molten state and is rocks that are inside the Volcano.
Lava is the same magma when it flows out of a volcano during a volcanic eruption.
So, there is a difference, and it is based on where this fiery substance is found..
It is called Magma, if it's under the surface of the Earth.
It's called Lava, when on the surface, hope that clears the doubt..