Use cases of docker
Docker has various applications, it can be used to host production websites/applications/Database etc. and in result they use very less system resources.
Also, their wide use case is actually at the time of testing application/website.
For eh- Let’s say you have to test ISL functionality of Apache, instead of using virtualization and installing guest OS once can simply install docker and launch Apache app as a service within one of the containers and check for SSL configurations.