What's the difference between a caste system and a social system?

martin luther king (1929-1968) was an activist for the african american rights, mr. king has a profile of a kind leader that built a tenacity, respect and full of hope future. he was an activist through civil disobedience and no violence pressure mechanisms. he tried to build a more egalitarian and fair society. his efforts carried a reivindication message of the civilian rights to every west corners. for that reason, he won the nobel prize in 1964.