We often use ‘simple’ and ‘easy’ interchangeably. This presentation given by Rich Hickey makes it clear about the difference between the two words. Simple is objective. Easy is relative. Some thing may be very easy to someone, but very hard to others. When we say something is easy, it might be because we are familiar with it. It doesn’t necessarily means it is simple.

http://www.infoq.com/presentations/Simple-Made-Easy