Dúvida sobre UserService

Olá,

Gostaria de saber qual é o papel do UserService no código da aula:

import { Directive, ElementRef, Input, OnInit, Renderer } from '@angular/core';
import { UserService } from 'src/app/core/user/user.service';
import { Photo } from '../../photo/photo';

@Directive({
    selector: '[photoOwnerOnly]'
})
export class PhotoOwnerOnlyDirective implements OnInit {

    @Input() ownedPhoto: Photo;

    constructor(private element: ElementRef<any>,
        private renderer: Renderer,
        private UserService: UserService) {}

    ngOnInit(): void {
        this.UserService
            .getUser()
            .subscribe(user => {
                if(!user || user.id != this.ownedPhoto.userId)
                    this.renderer.setElementStyle(this.element.nativeElement, 'display', 'none')
            })
    }
}