Image masking also a background remove technique. Before I told you that removing background is easy but not always. Sometimes we get images which edges have fur or hair, that time it become difficult to remove background. So that kind of situation we use a technique which called Masking.
In photoshop there is different kinds of masking techniques. In these cases mostly we use layer mask and use refine mask to remove background from edges.
Its very important to do perfectly remove background and keep each details of the images. Because good images attracks more customer and can increase the probablity of sale.