Is there any difference between REST Assured and RESTful web services?
REST stands for Representational State Transfer, which is an architectural style for distributed hypermedia systems, frequently used to build web services that aim to be lightweight, maintainable and scalable.
The REST architecture was defined by Roy Thomas Fielding in his dissertation and should follow this set of constraints:
The fundamental concept in a REST architecture is the resource and resources can have different representations. For more details, this answer can be helpful.
It's also worth mentioning that the REST architectural style is protocol independent but it's frequently designed over the HTTP protocol because it is largely adopted and well known.
A service based on the REST architecture, following the constraints mentioned above, is called RESTful.
REST Assured is a tool that aims to bring simplicity for testing and validating the response of REST services in Java.