My formal answer is that it is really about the rigor and perseverance required to solve problems. My simple answer is that common core is about deeper thinking.
For example, we used to teach kids how and where to find the answer to a problem. We would go the the textbook or encyclopedia and look up the answer. Today, there are a multitude of places to find the answer. We can easily use the internet on our telephone!
Since technology is so accessible to find information, our job today is to teach kids how to be thinkers and problem solvers. The common core standards require students to find the information and then apply it to real life situations. These are much more challenging lessons, but they truly prepare students for the future jobs that haven't even been created yet.