Countable infinity

Countable infinity refers to a type of infinity that can be matched one-to-one with the natural numbers (1, 2, 3, ...). This means that, even though there are infinitely many elements, you can list them in a sequence. Examples include the set of whole numbers or rational numbers (fractions). In contrast, uncountable infinity, like that of real numbers, cannot be listed this way; there are more real numbers than whole numbers. Essentially, countable infinity is a manageable kind of infinity, where we can still "count" the elements, even though the counting goes on forever.