How to retrieve data from a GeoServer?

Below is the compilation of information from various sources, mostly ArcGIS help. Wisely speaking, this one is not very well structured. There are many questions that juggling here and there. So I try to grab only essential information. This only serves the questions that pop up in my mind. So here we go :

What is Geoserver?

GeoServer is a Java-based software server that allows users to view and edit geospatial data. GeoServer is massively used for the purpose of map creation and data sharing. Simply put, you can share, edit, connect and…