Docker volumes vs configs?

I start under docker and I do not understand the difference between volumes and configs.

https://docs.docker.com/compose/compose-file/#volumes-top-level-element

https://docs.docker.com/compose/compose-file/#configs-top-level-element (added in version 3.3 of docker compose)

Should the configs properties be defined if, for example, a configuration file is used on different services ?

In what case does it apply ?

For example to share the Apache Root Document (/usr/local/apache2/htdocs) with volumes :

version: '3.8'

services:

  apache:
    image: httpd:2.4
    restart: always
    ports:
      - 8000:80
    volumes:
      - ./:/usr/local/apache2/htdocs
      - php-socket:/run/php
    depends_on:
      - php-fpm
    networks:
      - code

  php-fpm:
    image: php:7.4-fpm
    restart: always
    ports:
      - 9000:9000
    volumes:
      - ./:/usr/local/apache2/htdocs
      - ./.docker/php-fpm/zz-docker.conf:/usr/local/etc/php-fpm.d/zz-docker.conf
      - php-socket:/run/php
    networks:
      - code

volumes:
  php-socket:

networks:
  code:

What is the difference with the configs properties ? :

version: '3.8'

services:

  apache:
    image: httpd:2.4
    restart: always
    ports:
      - 8000:80
    volumes:
      - php-socket:/run/php
    configs:
      - source: apache-www
        target: /usr/local/apache2/htdocs
    depends_on:
      - php-fpm
    networks:
      - code

  php-fpm:
    image: php:7.4-fpm
    restart: always
    ports:
      - 9000:9000
    volumes:
      - ./.docker/php-fpm/zz-docker.conf:/usr/local/etc/php-fpm.d/zz-docker.conf
      - php-socket:/run/php
    configs:
      - source: apache-www
        target: /usr/local/apache2/htdocs
    networks:
      - code

volumes:
  php-socket:

configs:
  apache-www:
    file: ./

networks:
  code:

The two examples above work, But I don’t understand the difference between volumes and configs ?

Can anyone explain to me ? Thanks !