Declare a type alias just like declare a variable
Just like we can use variable declarations(let, var, const) to declare a variable that aliases to a value, we can declare a type alias that points to a type.
type Age = number;
type Person = {
name: string,
age: Age
}
let age:Age = 5;
let driver: Person = { name: 'Jump Roper', age: age };
type Color = 'red'; // a type aliases to a type literal
let color:Color = 'red';
Whenever we see a type alias used, we can substitute in the type it aliases without changing the meaning of the program.