A comparison operator is a symbol used in programming and mathematics to compare two values or expressions. Common comparison operators include greater than (>), less than (<), equal to (==), and not equal to (!=). These operators help determine the relationship between values, such as whether one number is larger than another or if two strings are identical. In programming languages like Python, Java, and C++, comparison operators are essential for controlling the flow of a program. They are often used in conditional statements, such as if statements, to execute specific code based on whether a condition is true or false.