A cardinal number is a number that indicates quantity. It answers the question "how many?" and is used for counting objects. For example, the numbers 1, 2, 3, and 10 are all cardinal numbers because they represent specific amounts of items. In contrast to ordinal numbers, which indicate position or order (like first, second, or third), cardinal numbers focus solely on the size of a set. They are fundamental in mathematics and everyday life, helping us quantify things like the number of apples in a basket or the total number of students in a classroom.