When to use Interface and Model in TypeScript Angular

Question

I recently watched a Tutorial on Angular 2 with TypeScript, but unsure when to use an Interface and when to use a Model for data structures.

Example of interface:

export interface IProduct {
    ProductNumber: number;
    ProductName: string;
    ProductDescription: string;
}

Example of Model:

export class Product {
    constructor(
        public ProductNumber: number,
        public ProductName: string,
        public ProductDescription: string
    ){}
}

I want to load JSON data from a URL and bind it to the Interface/Model. Sometimes I want a single data object, other times I want to hold an array of the object.

Which one should I use and why?