An infinite set is a collection of elements that has no end or limit. Unlike finite sets, which contain a specific number of items, infinite sets can be counted indefinitely. For example, the set of all natural numbers 0, 1, 2, 3, ... is infinite because you can always add one more number. There are different types of infinite sets. Some, like the set of natural numbers, are countably infinite, meaning their elements can be matched one-to-one with the natural numbers. Others, such as the set of real numbers x | x is a real number, are uncountably infinite, indicating that they cannot be listed in a sequence.