what is federalism?

what is federalism? what is federalism?英文回答 what are the features of the federalism?请简要用英语回答~100~150字 the form of the united states goverment is based on three main principles,federalism ,theseparation of powers and respect for the constitution and the rule of-----?这最后一个是什么啊? What is what is what is? what is What is what is what is what is what is what is what is what is what is What is