There are two kinds of constructions in C++ programs. Executables directly lead to machine language code and non-executables that affect the machine language of the executables.
Non-executables are usually declarative. That is, they indicate the properties or presence of things that will be later used by the executables. For example, include statements are not executable. They make available libraries of executables, but do not cause any execution directly. The function header:
int main () {
does not cause any execution but describes the properties of the main function.
Executable statements cause an action, either within the program or visible outside. For example:
cout << "Hello World!"
causes this string, without the quotes, to be displayed on the console.