Web parts are ASP.NET controls that can be added to web part zones. They are generally distributed as WSP files. Pre-2013, they could be developed off the hosting server. With 2013, WebParts for the most part have to be developed the hosting server for proper library inclusion.
I created a webpart that is able to consume a service provided by Dynamics NAV 2009 R2. I documented in short what I did so far: http://shb.vps.bitfolk.com/nav-sharepoint.html I use the following ...