Core Java is an object oriented programming language, which has easy syntax and functions. Most of the syntax are in simple English, hence a common user can figure out what the syntax means and learn the language easily. Due to these reasons, Java programmers are able to write programs in a shorter time frame.
Advance Java-Advanced JAVA is like learning frameworks which have already built. Day by day , company to company and project to project,, the framework that you will be using might get changed. The core concepts that you use will never get changed.