Whats the difference between the variable and comstant

Question

if we write a variable for example like this
int my age
how should we write a constant

Answer 1

const int my_age = 43;

Variable names shouldn't contain a space. Well, any identifier shouldn't contain a space.

Answer 2

a variable can change its value during the execution, a constant cant, in fact, a constant during the compiling is processed by the precompiler. this means that before the compiler all constants are change to its value

Answer 3

and constant names can contain a space or what?

Answer 4

sebipincha
i understand but why in lesson 2 they wrote int myage=34
the age can be changed cause its a variable