What are auto deployment and pipelines, and how to get started?

I'm still not sure what pipelines are. Automatic testing? Can it be used for auto deployment to 1) Sandbox/test server 2) produciton server when ready?

I need to create some configuration files, but I feel I don't understand what it really is that I need to use, what it can deliver and how I should use it.

Any good resources on gettings started with pipelines but also how to automate my deployment through GitLab?