I am trying to learn angular 6, and I've come across a line of code that I don't think is well explained. It isn't producing any significant changes when being removed from the code, but is in a tutorial that I've been following. Please clear up what the following line of code does in this html file.

[class.selected]="atype === selectedType"

Full html code:

<h2>My Types</h2>
<ul class="types">
  <!-- Create the for loop, and then assign the selected element to the current type. -->
  <li *ngFor="let atype of types"
    [class.selected]="atype === selectedType"
    (click)="onSelect(atype)">
    <span class="badge">{{atype.id}}</span> {{atype.name}}
  </li>
</ul>

<div *ngIf="selectedType">

  <h2>{{selectedType.name | uppercase}} Details</h2>
  <div>
    <span>id: </span>{{selectedType.id}}</div>
  <div>
    <label>name:
      <input [(ngModel)]="selectedType.name" placeholder="name">
    </label>
  </div>

</div>

types refers to an array.