earth style is the using or creation of rock, stone, mud, dust or earth it self encompassed in the ninja's chakra itself. the earth is, by definition, solid minerals combined. the relation to a ninja is that, firstly, the ninja trains and gets better on it and then is where we live hence is eveyrwhere making it a valuable weapon for a ninja if he/seh knows how to use it.
even though earth is sturdy, it's weak to raiton or lighining based moves. the doton jutsus are strong against water-nature techiniques.