What are services in a docker-compose file?

The services section in a docker-compose file is an array of containers which are to be built and run together when the docker-compose file is executed. Each container under a docker-compose file is indicated with a user specific "service_name" which is used by other containers for communication among themselves. These "service names" need to be unique within a docker-compose file and are auto resolved for their respective containers by the docker.

version: '3'
services: 
    redis-server:
        build: .
        ports:
            - 8000:6379
     angular-app:
        build: .
        ports:
            - 8080:80