Theory:

The rocks are the naturally occurring solid materials or the agglomeration of minerals forming the earth’s crust or lithosphere. The word ‘lithosphere’ means a ‘sphere of rock’ or ‘rock sphere’.  These rocks are made up of single or more minerals.
A rock does not necessarily look like a hard, massive-sized stone; at times, it may be soft small textured particles like mud, clay, sand etc. A small unit of the rock is called an element.
 
The rocks based on the origin are categorized into three major types: Igneous, Sedimentary and Metamorphic.
 
rock types.png
 
rocktype.png
Reference:
https://www.open.edu/openlearn/science-maths-technology/science/geology/rock-types