What is a service in Angular and when would you use one?

A service is a class with a specific purpose that provides functionality not directly related to views. Services are used for:

• Data sharing between components
• Business logic that shouldn't be in components
• External communication (HTTP requests)
• Utility functions and helpers
• State management

Creating a service:

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

@Injectable({
  providedIn: 'root'
})
export class DataService {
  private data: string[] = [];

  getData(): string[] {
    return this.data;
  }

  addData(item: string): void {
    this.data.push(item);
  }
}