Those two refer to the ways people can receive a nationality of the country. Law of Soil, or Jus Soli, as it's often called means that all people born on certain soil have the nationality (this is true for the US) and Law o Blood means that you need to be a descendant of a citizen - you can be a citizen without ever having been to a country (also called Jus sanguis, and is the case in European countries).
