Angular5 @output decorator

Hello there learning angular and came across the @output decorators in angular. After researching the topic I still have some difficulty wrapping my head around this concept.

Code example:

app.component.html:

<app-tutorials(event)="doSomething($event)"></app-tutorials>

app.component.ts:

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

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

  doSomething(event){
    alert("being executed");
  }
}

tutorial.component.html:

<button (click)="beingClicked($event)"_>click me</button>

tutorial.component.ts:

import { Component, OnInit, Output, EventEmitter } from '@angular/core';

@Component({
  selector: 'app-tutorials',
  templateUrl: './tutorials.component.html',
  styleUrls: ['./tutorials.component.css']
})
export class TutorialsComponent{

  @Output() event = new EventEmitter();

  beingClicked(event){
    this.event.emit(event);
  }
}

My current understanding is this, plz correct me if I'm wrong:

• output is used to transfer data only from child components the parent component.
• When the button is clicked beingClicked(event) is fired and passes through event info in the argument with $event.
• We can emit the event with this.event.emit(event); because we first instantiated the event earlier in the class with the statement: @Output() event = new EventEmitter();
• Now the parent component listens for (event) in the app.component.html:<app-tutorials(event)="doSomething($event)"></app-tutorials>
• When the event is emitted from the child component the doSomething($event) function is fired and gets passed in the $event

Question:

1. Is my current understanding correct?
2. What exactly is this EventEmitter and is it always needed to data upwards?