Its really hard to summarize what is NDepend in few words as this tool does a lot and its really useful when you have a big project and had to do code analysis, code usage, code metrics etc., etc., So, to make things simpler, lets take what their website says
NDepend is a tool that simplifies managing a complex .NET code base. Architects and developers can analyze code structure, specify design rules, plan massive refactoring, do effective code reviews and master evolution by comparing different versions of the code.
With NDepend you can analyse a set of .NET assemblies and that was the first step for me in using NDepend. Another highlight of NDepend is that you can use Code Queries to query to analyse and get results. More on Code Query Language here.
The Repository Factory is a guidance package that automates creation of entity classes that map to database tables and repository classes to read and write those entity classes. The generated code removes the tedium of writing a persistence-ignorant domain model.
You could get more information, discuss and download the Repository Factory here