The expression "5 + 3" represents a simple addition problem in mathematics. In this case, the number 5 is combined with the number 3 to find the total. Addition is one of the basic operations in arithmetic, which is a branch of mathematics that deals with numbers and their relationships. When you add 5 and 3, you count up from 5 by 3 more. This results in a total of 8. Therefore, the answer to the equation "5 + 3" is 8. This concept is fundamental in math and is often one of the first operations taught to students.