In C++, an expression is a combination of literals, variables, operators, and function calls that evaluates to a single value. A statement is a unit of code that performs a specific action, such as assigning a value to a variable, calling a function, or controlling the flow of execution.

Expressions can be used to perform computations, compare values, or perform logical operations. For example, the following are examples of expressions in C++:

int x = 10;
int y = 20;
int z = x + y; // Adds x and y, evaluates to 30
bool result = (x > y); // Compares x and y, evaluates to false

Here, the expression "x + y" adds the values of "x" and "y" and evaluates to 30, while the expression "(x > y)" compares the values of "x" and "y" and evaluates to false.

Statements are used to perform actions such as assigning values to variables or calling functions. For example, the following are examples of statements in C++:

int x = 10; // Assigns the value 10 to the variable x
cout << "Hello, world!" << endl; // Calls the cout function to output a string to the console
if (x > 5) { // A conditional statement that checks if x is greater than 5
    cout << "x is greater than 5" << endl;
} else {
    cout << "x is less than or equal to 5" << endl;
}

Here, the first statement assigns the value 10 to the variable "x", the second statement calls the cout function to output a string to the console, and the third statement is a conditional statement that checks if "x" is greater than 5 and outputs a message to the console accordingly.

In summary, expressions are combinations of literals, variables, operators, and function calls that evaluate to a single value, while statements are units of code that perform specific actions such as assigning values to variables or calling functions.