A surname is like a family name that people have in order to identify themselves as part of a certain family. Like your parents have their own last name, and you have the same last name as them. Loza is a surname that some people have. It might have originally come from someone's ancestor who had that name or it could have been chosen by the family at some point in time. But basically, it's just a last name that helps people know who you are related to.