Thank you Bear and Stephan. As per my understanding, we can handle HTTP GET/POST/DELETE/PUT requests using servlets as well as REST services. So, just thinking what makes them different? And, for REST services also, I believe they first hit the servlets only e.g. JerseyServlet for Jersey implementation, dispatcherservlet in case of Spring REST.
Servlets are a general-purpose request/response mechanism built in Java. REST is a convention for data interchange. Sure, you could use servlets to build a REST API, but that doesn't make them the same thing.
It's like asking what the difference is between a pile of bricks, and a brick house. The bricks can be used to build the house, but you can't say that the bricks and the house are interchangeable.