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 "a" and "b" 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, along with subtraction, multiplication, and division. It is commonly used in everyday life, such as when calculating expenses or combining quantities. Understanding "a + b" is fundamental to more complex mathematical concepts and problem-solving.