What is a Service?
https://en.m.wikipedia.org/wiki/Server_(computing)
Server client vs peer to peer
Within web based services, this often means features that can be accessed by creating a user account. For some services, there are a single user, whereas others low for true multiuser environment. Services will often have their own interface, especially within a browser. Some may need to be configured through files, but many work with gui configuration.
Integration with Authelia, reverse proxy.
In relation to SaaS
https://en.m.wikipedia.org/wiki/Software_as_a_service
Docker vs service vs port
Free freemuim, subscription, usage based
Funding, advertising, selling consumer data
Many services offer apis
Federation
These remove the control of software from users and make them subscription based. You can't own a CD with the service available for install. There is only one version of the app, hosted by the service provider. Even extension apps only interact with the current version through API.
https://en.m.wikipedia.org/wiki/As_a_service
As a service business model, subscription based instead of something owned