Too Long; Didn't Read
Angular is based on components, so if you start to create a page in angular you should split this page into small components. The last version of angular is @9, but I will show definitions to communicate in all angular versions, probably it will be in the angular platform for a long time. In the next image, there are some components and examples of how you need to communicate with parents with children, siblings, child to parent, and more cases. In summary, you can create a service and you should inject this service in each component to share information.