code which is written in respective languages ( VC++ , C#, VB.NET or J#) will generates MSIL(Microsoft Intermediate Language) code by it's compilers. Then CLR will convert MSIL code to executable code when the program runs. 

The core functions of CLR are

Unmanaged code : code which is not executed under .NET runtime (CLR). CLR is does not have control over execution of code.memory management, security and type safety should be taken care by developer.  

E.g: VB6, C,C++. 

managed code typically compiled to Intermediate Language(IL) code where as unmanged code directly compiles to native code.

When we run the program, Common Language Runtime(CLR) will translate MSIL code to executable code. CLR will covert MSIL code from any of .NET language.

A content database is a database file that stores content for one or more site collections for SharePoint web application. The content can be pages,files,documents,images and much more. So if the Site Collection has more number of SharePoint sites, the content database size grows rapidly.

One SharePoint web application can have more than one content database mapped to it and the max limit is 300 ContentDB's per Web Application. If you want to add more content databases to web application, Go to Central Admin -> Application Management -> Manage Content Databases -> select web application -> Add a content database.

Maximum Content database size is 200 GB in general usage scenarios.

Service Applications(SA) are software services which run in a SharePoint farm. These are very useful to share information, resources and capabilities across multiple sites/applications/servers in the same share point farm or even across farms.

Service applications are introduced from SharePoint 2010. Advantage with the Service Applications are salable and extensible.

Sample Service Applications:

Access Services

User Profile Service

User Profile Synchronization Service

SharePoint Server Search

...

Location of services : Central Administration -> System Settings -> Manage services on server

Site Template is a pre-defined set of configuration, layout, and content files that define a site model for an SharePoint application. In built SharePoint has shipped with the set of site templates or we can create our own site templates. 

Each site collection site is associated with a site template. While creating a new site collection for an web application from Central Admin, we need to select a site template from Template Selection section.

Once we crate site collection, share point stores some of the files in the file system of front-end webs servers and some content in back-end databases. When we request for a page from browser, SharePoint engine will decide from where it needs to pick the data either file system or content database.

Collaboration - Team Site

Collaboration - Blog

Collaboration - Coommunity Site

Enterprise - Document Center

Publishing - Publishing Portal

Publishing - Enterprise Wiki

SharePoint site has different permission levels for the SharePoint Groups. When you create SharePoint site, you can observe the below permissions as default. 

Full Control - Has full control.

Design - Can view, add, update, delete, approve, and customize.

Edit - Can add, edit and delete lists; can view, add, update and delete list items and documents.

Contribute - Can view, add, update, and delete list items and documents.

Read - Can view pages and list items and download documents.

Limited Access - Can view specific lists, document libraries, list items, folders, or documents when given permissions.

Approve - Can edit and approve pages, list items, and documents.

Manage Hierarchy - Can create sites and edit pages, list items, and documents.

Restricted Read - Can view pages and documents, but cannot view historical versions or user permissions.

Restricted Interfaces for Translation - Can open lists and folders, and use remote interfaces.

We can create our own set of permissions also. In order to create new permission, go to site settings -> Users and Permissions -> Site permissions -> Permission Levels(Display list of permissions avalible on site) ->  Add a Permission Level

Inbuilt SharePoint provides some predefined list of templates like Announcements,Calendar,Picture Library,Links...etc. If none of templates are meeting you requirement, you can create your own custom list instance and define columns/views for the list. This list is called Custom List.

In-order to create new custom list, Go to Site Contents -> Add an App -> Select Custom List -> Provide Name for Your Custom list.After creating list, add columns and views to it.

Create Column/View for List: Open created Custom List -> List Settings -> Create Column/View

Note: By default every Custom List will have 5 columns (Title, Modified, Created, Created By and Modified By).

When we create a Custom List in SharePoint site, By default 5 columns are added to custom list which are

We can modify the column properties by clicking on Column Name from List Settings.

When we create a Custom List in SharePoint site, we need to map the list to View. By default when we create List, it will be mapped to "All Items" standard view. But we can change the view for the list. 

Each view is created from View Type and below are the available view types

In order to see the available view types, Go to Custom List Settings -> Create View -> View Type.