About CRM programming environments and skills with class tree structure diagram such as IOrganization Service, IDiscoveryService,

I am just learning CRM with trial version of Microsoft Dynamic 365 for Customer Engagement, I need help from all experts, I appreciate if any expert can correct me and add or change my following findings:

so far, to make it simple, I found that the program coding environment basically includes:

1. Client side object model (Xrm.Page Object Model) which uses JScripts, and combined with HTML, CSS, xml, images etc.

2. Server side programming, basically writing different plugIns using IOrganizationService and IDiscoveryService using C# or VB

Is my understanding right, can anybody correct me or add more of it?

Many programs have their class diagram as a tree structure, so I can put it on the wall in office for reference daily,

does anybody have resource links or PDF document of CRM program class (Object) diagram, basically, we can see all classes in one diagram overview?

Thanks a lot