The expression "3 + 5" represents a simple addition problem in mathematics. In this case, the number 3 is combined with the number 5 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 3 and 5, you count up from 3 by 5 more. This results in a total of 8. Therefore, the solution to the equation "3 + 5" is 8, which can be visualized as having three apples and then adding five more apples, resulting in a total of eight apples.