A very basic and overview which can solve your initial queries :
What is the Lightning Component Framework?
-> The Lightning Component framework is a UI framework for developing dynamic web apps for mobile and desktop devices.
-> The aura namespace contains components to simplify your app logic, and the ui namespace contains components for user interface elements like buttons and input fields
Visualforce and Lightning Comparison
-> Lightning components are client-side focused, making them more dynamic and mobile
-> Visualforce components are page-centric and rely heavily on server calls.
-> Lightning components use Apex on the server side, organizations that can’t use Apex code can’t create Lightning components, but they can use Visualforce
-> You don't have to spend your time optimizing your apps for different devices as the components take care of that for you.
-> The framework uses JSON to exchange data between the server and the client.
-> Components are the self-contained and reusable units of an app.
-> You can use Developer Console to build lightning apps and components
Aura and Lightning?
-> Lightning components are based on the open source Aura framework available at https://github.com/forcedotcom/aura.
-> The Aura framework enables you to build apps completely independent of your data in Salesforce.
Many more to come to get you started with lightning, stay tuned.