The expression "a + b" represents a simple mathematical operation known as addition. In this context, "a" and "b" are variables that can stand for any numbers. When you add these two values together, you find their total or sum. For example, if a is 3 and b is 5, then a + b equals 8. Addition is one of the four basic arithmetic operations, alongside subtraction, multiplication, and division. It is commonly used in everyday situations, such as calculating expenses or combining quantities. Understanding "a + b" is fundamental to more complex mathematical concepts and problem-solving.