Seam Carvinng is an algorithm for content aware resizing. It was developed by Ariel Shamir and Shai Avidan in the paper Seam Carving for Content-Aware Image Resizing. The major need for seam carving is that it is hard to preserve the features of the image across several devices. Before seam carving was introduced most devices try to fit the image on a display by either scaling and stretching or by cropping the image. The final shape of image on display is not predictable with those methods and there are chances that cropping might delete some major parts of the image while stretching or scaling might create some artifacts.
For example lets say if someone wants to resize the image shown below: IMAGE