The expression "x + 3" represents a simple algebraic equation where "x" is a variable that can take on different numerical values. The "+ 3" indicates that 3 is added to whatever value "x" represents. This expression is often used in mathematics to illustrate how changing the value of "x" affects the overall result. In practical terms, if you substitute a specific number for "x," you can easily calculate the outcome. For example, if x equals 2, then "x + 3" would equal 5. This concept is fundamental in algebra and helps in solving equations and understanding relationships between numbers.