Why are there 4 types of lava?

Could you please explain the reasoning behind the existence of four distinct types of lava? I'm curious to know what geological or volcanic processes give rise to these variations in lava composition and characteristics. Do the different types of lava have any implications for volcanic activity, such as the intensity or frequency of eruptions? Additionally, how do scientists classify and identify these types of lava in the field? I'm eager to gain a deeper understanding of this fascinating aspect of volcanology.