What is the concept behind anime?
It's just a type of animation, there really isn't much of a concept. It's just like Fairly Odd Parents style or 3D/animated cartoons, or the seemingly hand-drawn Ed Edd and Eddy; just an animation style.
However, after Asian countries produced most of the anime shows, people started to stereotype them saying "ITS ALL ROBOTS AND MAGIC GIRLS". Even when they stopped producing those generic types of shows, the stereotype stayed.