Salesforce lightning : What has changed

This is same question which popped in my mind. 

• What has changed? 
• What happens to my previous development work if I turn on Lightning experience.
• Do I need to rewrite my Apex classes, VF pages, buttons etc.

Well, the first thing calm down! All your stuffs are right there and most of it will work fine with a few modifications and yes there are some exceptions which I will cover in the upcoming posts.

P.S. Lightning is evolving fast i.e. if it is not supported yet, it will be very soon.

Salesforce is moving from page-centric web application model to app-centric model. You may ask what benefits can we reap from this approach. Here are some of the magic of app-centric model:

• Isolated/resuable components: It allows us to create isolated components i.e. you can create a component and 'drag and drop' anywhere without any modifications at all. Tell me more.
• Interactive experience: To deliver it we need client side scripting. Lightning uses Javascript to create, modify, transform, and animate the user interface rather than completely replacing it a page at a time. 
• Faster loading: The components are standalone and uses client side scripting. This helps in minimizing server calls resulting in improved performance.