The expression "3 x 4" represents a multiplication problem where the number 3 is multiplied by the number 4. In this case, 3 indicates that there are three groups, and each group contains four items. When you calculate "3 x 4," you find the total number of items in all groups combined. The result is 12, meaning there are twelve items altogether when you have three groups of four. This concept is fundamental in mathematics and is often used in various real-life situations, such as counting objects or organizing items.