you might have heard lots of stuff about responsive design and trends for developing and designing website. IF you are beginner knowing and utilizing responsive images would be first step towards creating responsive web design. Making your images responsive, you would reach at around 30 %of task in making its design responsive. a nice article has been written at alist apart.com which you can have a look at below link.
http://www.alistapart.com/articles/responsive-images-how-they-almost-worked-and-what-we-need/