I want my homepage to be replaced when I click on a link to another page, but instead, the other page is added to my home

I am trying to add a second page to my web app, but instead, the second page's HTML is added to my homepage. Why?

app-routing.module.ts

import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';
import { OtherPage } from './app.other-page';

const routes: Routes = [
  { path: 'otherpage', component: OtherPage },
];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})
export class AppRoutingModule { }

app.component.html

<!--The content below is only a placeholder and can be replaced.-->
<div style="text-align:center">

<h1 *ngIf="'test' === str">It's true!</h1>

<a [routerLink]="['/otherpage']">Go to Other Page</a>

<router-outlet></router-outlet>

app.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css'],
})
export class AppComponent {
  title = 'angular-test';
}

app.other-page.html

 <h1>This is the other page</h1>

app.other-page.ts

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.other-page.html',
})
export class OtherPage {
  title = 'angular-test';
}

In the example code: the "Go to other page" link is still on the page when clicked, while I'd rather the other page consist of only app.other-page.html.