what is interface in angular code example

Example 1: ts interface optional parameter

interface Person {
    name: string;
    age: number;
    phone?: string;
}

let p: Person = {name: "Ashlee", age: 29};
console.log(p);

Example 2: typescript interface function

interface IEmployee {
    empCode: number;
    empName: string;
    getSalary: (number) => number; // arrow function
    getManagerName(number): string; 
}