Make a Free-Form Selection?

If you want to select something that isn’t square, maybe an object in your image, you need to make a free-form selection (a selection that isn’t square [or round]) using the Lasso tool (its icon looks like a rope lasso). Just choose it from the Toolbox (or press L) and trace along the edges of the object you want to select. If you need to add to the selection (once you’ve drawn it), press-and-hold the Shift key and keep tracing. Anything you trace around while you’re holding that Shift key gets added to what you already selected. If you make a mistake and trace around an area you didn’t mean to (you “painted outside the lines”), then press-and-hold the Option (PC: Alt) key instead, and trace around the area you want to remove. To deselect your selected area, press Command-D (PC: Ctrl-D).