Expressions can, at times, be confusing to understand. Expressions often look very similar to program statements, so it can be difficult to distinguish a statement from an expression, and so on. Expressions are written to be evaluated at runtime before returning a value; the value can only be ascertained at runtime. Statements, however, are program code that are executed to perform an action, such as assignments and looping. An expression is comprised of variables, operators, literals, and functions that work together to generate runtime values.
Generally, we declare variables using a specific data type and then use that variable at multiple points within the program. Expressions are similar to variables; however, the variable itself is instead constructed and evaluated at runtime.
Let's understand expressions with the help of an example, as follows...