Large Cardinals are a special type of infinite cardinal number in set theory, a branch of mathematics. They extend the concept of cardinality, which measures the size of sets, particularly infinite sets. Large Cardinals are defined by certain properties that make them "larger" than other infinite cardinals, such as the ability to support certain types of mathematical structures and theories. These cardinals are significant in the study of the foundations of mathematics, particularly in relation to the Axiom of Choice and Zermelo-Fraenkel set theory. They help mathematicians explore the limits of set theory and the nature of infinity, leading to deeper insights into the structure of mathematical objects.