What is the difference between data abstraction and encapsulation?

Data Encapsulation : It is a process of bundling the data, and the functions that use them, as a single unit( atleast in C++) . In C++ the data type "class" is used to achieve this.

Data Abstraction : It is a process of exposing only the interfaces and hiding the implementation details from the user. The interface exposed will remain the same: even if the internal implementation changes. This helps the user to use the new functionality without rewriting the client that was designed for previous implementation (strictly speaking ... previous interface).