Some more examples besides #c-snover's answer from here. You can put them together.

import 'jquery';                        // import a module without any import bindings
import $ from 'jquery';                 // import the default export of a module
import { $ } from 'jquery';             // import a named export of a module
import { $ as jQuery } from 'jquery';   // import a named export to a different name
import * as crypto from 'crypto';       // import an entire module instance object

export var x = 42;                      // export a named variable
export function foo() {};               // export a named function

export default 42;                      // export the default export
export default function foo() {};       // export the default export as a function

export { encrypt };                     // export an existing variable
export { decrypt as dec };              // export a variable as a new name
export { encrypt as en } from 'crypto'; // export an export from another module
export * from 'crypto';                 // export all exports from another module
                                        // (except the default export)

You just import it normally and the compiler works out that you don't need the import statement emitted because no concrete code is used.

Here's an example:

component.ts

export interface MyInterface {
    name: string;
}

app.ts

import { MyInterface } from './component';

class MyClass implements MyInterface {
    constructor(public name: string) { }
}

The app.js file is simply (ES2015 version):

class MyClass {
    constructor(name) {
        this.name = name;
    }
}

Or in older ES5 terms:

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
var MyClass = /** @class */ (function () {
    function MyClass(name) {
        this.name = name;
    }
    return MyClass;
}());

The important thing here is that the TypeScript compiler has worked out that the import is only needed at compile time, not runtime.