Fissure eruptions are one type of volcano and are found at conservative plate margins ie. where two plates move apart from each other. They are seen as an elongated crack of the surface crust and an example is the Mid-Atlantic Ridge and underneath the Atlantic Ocean. As the plates move apart, basaltic (basic) lava is able to rise and erupts through the crack. [First type] Shield volcanoes are another type of volcano and these have gently sloping sides. This is because basic lava is also erupted from these which is less viscous and can therefore flow much further and faster before it cools and hardens. Shield volcanoes are found at destructive plate margins where oceanic crust is subducted under continental crust. An example of one is Mauna Loa in Hawaii which is the biggest volcano in the world and is found at a hotspot. [Second type, plus good example. Level 2 now]
Composite stratovolcanoes are found at destructive plate margins and have much steeper sides than shield volcanoes. This is because the lava erupted from them is andesitic intermediate and so flows less easily as it is more viscous. Therefore if can not travel as far, resulting in the steep sides of the volcano. An example of this is Mount Fiji and also Mt Etna in Sicily. These therefore have more explosive eruptions as the thicker more viscous lava builds up until a large amount of pressure causes it to erupt. [Third type, plus example]
Calderas are another type and these again have steep sides due to more