Q:

Angular2 Routing: Would there be a condition that the link parameters array would have more than one element?

I'm teaching myself Angular2.  The text I'm reading says the following: When the user navigates to the a feature that’s tied to a route with the routerLink directive, the router uses the link parameters array and the route configuration to compose the URL segment. 
The code example given: 
import { Component } from 'angular2/core';
import {ProductListComponent} from './products/product-list.component';
import {ProductService} from './products/product.service';
import {HTTP_PROVIDERS} from 'angular2/http';
import {ROUTER_PROVIDERS, RouteConfig, ROUTER_DIRECTIVES} from 'angular2/router';
import 'rxjs/Rx'; //Load all features
import {WelcomeComponent} from './home/welcome.component'
@Component({
    selector: 'pm-app',
    template:`
    <div>
        <nav class='navbar navbar-default'>
            <div class='container-fluid'>
                <a class='navbar-brand'>{{pageTitle}}</a>
                <ul class='nav navbar-nav'>
                    <li><a [routerLink]="['Welcome']">Home</a></li>
                    <li><a [routerLink]="['Products']">Product List</a></li>
                </ul>
            </div>
        </nav>
        <div class='container'>
            <router-outlet></router-outlet>
        </div>
    </div>`,
    directives: [ROUTER_DIRECTIVES],
    providers: [ProductService, HTTP_PROVIDERS, ROUTER_PROVIDERS]
})
@RouteConfig([
    {path: '/welcome', name: 'Welcome', component: WelcomeComponent, useAsDefault: true },
    {path: '/products', name: 'Products', component: ProductListComponent}
])
export class AppComponent {
    pageTitle: string = "Acme Product Management";
}

My question is:
Would there be a condition that the link parameters array would have more than one element?
It just seems to me like that would always be an array with one element only because it's tied to the name property in the RouteConfig obj which in turn is tied to the component that gets called to display it's content where router-outlet  directive is located.  If the answer is yes, would you explained how it is used.

A:

when you want to provide optional route parameters 
<a [routerLink]="['welcome', { foo: 'foo' }]">welcome</a>

Then you have more than one element in link parameters

