Do I need to create a dockerfile when using three docker-compose images?

Question

Docker

taking the first steps in learning docker and docker-compose. It's not entirely clear whether you need to write a dockerfile if you describe 3 or more images in docker-compose? If you don’t need to write what name and path you need to specify in docker-compose

, for example Laravel (there are more than 3 images here)
nginx:
dockerfile: docker/nginx.docker the path is specified, and it will appear from where, if I have, for example, UBUNTU and I installed docker and docker-compose there. It turns out that it was created through a dockerfile, or it is written like this docker/nginx.docker automatically uploads an image from dockerhub and I need to create a dockerfile.

version: '3'
services:
  nginx:
    build:
      context: ./
      dockerfile: docker/nginx.docker
    volumes:
      - ./:/var/www
    ports:
      - "8080:80"
    depends_on:
      - php-fpm
  php-fpm:
    build:
      context: ./
      dockerfile: docker/php-fpm.docker
    volumes:
      - ./:/var/www
    depends_on:
      - mysql
      - redis
    environment:
      - "DB_PORT=3306"
      - "DB_HOST=mysql"
      - "REDIS_PORT=6379"
      - "REDIS_HOST=redis"
  php-cli:
    build:
      context: ./
      dockerfile: docker/php-cli.docker
    volumes:
      - ./:/var/www
    depends_on:
      - mysql
      - redis
    environment:
      - "DB_PORT=3306"
      - "DB_HOST=mysql"
      - "REDIS_PORT=6379"
      - "REDIS_HOST=redis"
    tty: true
  mysql:
    image: mysql:5.7
    volumes:
      - ./storage/docker/mysql:/var/lib/mysql
    environment:
      - "MYSQL_ROOT_PASSWORD=secret"
      - "MYSQL_USER=app"
      - "MYSQL_PASSWORD=secret"
      - "MYSQL_DATABASE=app"
    ports:
      - "33061:3306"
  redis:
    image: redis:3.0
    ports:
      - "6379:6379"