This is a general answer not related to a specific programming language (as was the question). So the answer is: abstraction and encapsulation have nothing in common. But their implementations might relate to each other (say, in Java: Encapsulation - details are hidden in a class, Abstraction ... More on stackoverflow.com

I think abstraction is a more generic idea. To abstract is basically to produce a model of something that you want someone to use. For example, a road map is an abstraction for someone that only cares about roads. It doesn't try to capture, say, shops, terrain, how many lanes of traffic there is, etc. Encapsulation is more about hiding implementation details from you and to me, it's a form of abstraction. A real world example might be any electronic device you have, say, a TV remote control. There are buttons to increase the volume, decrease, change channels, etc. Most likely, these just produce infrared signals picked up by your television and the television understands what those signals mean. Maybe a better example is a car with a steering wheel, accelerator, and brakes. This is an abstraction, and the implementation is hidden away in the engine, etc. Indeed, it used to be the case that when you pressed the accelerator, it had a correlation with how much gas was used, but these days, the accelerator is read monitored by a computer, and the computer computes the most efficient way to provide the gas that lets you accelerate, but it can make better adjustments than a direct correlation to the amount of gas used. And, the same abstraction can be used for electric cars that don't use gas at all, yet, you can still have a steering wheel, accelerator, and brakes. More on reddit.com

Abstraction is basically the idea that the person who is working with a OOP class only needs to know the key information such as the what is the expected data going in and what is the expected results at the end of the call or what is returned.

So I have a function add(num1, num2) that I know it is expecting two numbers and I expect it to add those numbers together and it will return the result. How the adding is done is irrelevant to me (Abstraction). It also means if I decide to change the code on how the adding is done later, as long as the input and result/output remain the same, everything else in the program should work the same without missing a beat.

Encapsulation is basically the idea that the data within an OOP class will remain in that class and should not effect ANY thing else outside of the class. The data is essentially encapsulated. It is important to note that this also means that the functions data is safe from other functions (with exceptions, and depending on language) so you can always rely on the data being the way the class left it.

TL;DR: Abstraction is not caring how a function does, just what it does.

Encapsulation is knowing as long as the function is working properly, the data should be protected.

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class Foo { public: int length(); private: int begin; int end; }; begin and end are encapsulated. class Bar : public Foo { public: int min(); int max(); }; Bar inherits from Foo. int squareLength(Foo& foo) { int length = foo.length(); return length*length; } Bar bar; int baz = squareLength(bar); bar is passed to squareLength polymorphic. More on reddit.com