In the previous topic we talked about selections and represented the selected areas of an image with a series of lines. We also saw in the last lesson that the marquee didn't always accurately represent what was actually selected. If we applied a feather to the marquee, the selection would actually drop off over a range which could only be seen through the Quick Mask Mode (Q). Although it is easier to think of selections in terms of the marquee a more accurate and useful method exists through the use of masks.
In reality, there is really (or at least rarely) no such thing as a line. Zoom close in along the edge of an object in an image and you will see that instead of a line there is a transition zone of pixels. Your goal when selecting an object within an image is to capture this transition zone as closely as possible, if you do your object will look natural when the rest of the image is removed from it. If you don't your object will contain a border and will look unnatural.
