Igneous rocks come from volcanoes in one way or another. The word igneous comes from the Latin ignis, the word for fire. Magma will eventually either get shot out of the volcano as lava or it will cool very, very slowly inside the earth as magma. As magma cools, it crystalizes into rock. When magma is shot out of a volcano, it turns into lava, so magma is when it’s in the earth and lava is when it’s outside the earth. When the right kind of lava hits the right kind of water you get the coolest rock - obsidian. Ancient peoples preferred obsidian to make arrowheads for hunting game.