Advanced selections: the Marquee and Lasso tools
The Marquee Tool has two modes: Rectilinear and Elliptical—with these you can draw a square, rectangle, ellipse, or circular selection shape. In this exercise, I want to shift the door in the following image to the right, copy and paste the left-hand window over the space left by the [moved] door frame, and finally copy and paste an object from another image into the left-hand corner of this scene.
When making selections, it's important to appreciate that all selection tools work together—you can start with one, then if needed work with a second or third selection tool to complete the job.
Possibly the hardest task with selections is to determine which one is best for the job—here I started with the Rectangular Marquee Tool to make a selection of this house's front door: