Make Freeform Selections in Photoshop CS5
In Photoshop Creative Suites 5, the Lasso tool is used for making freeform selections (selections of an irregular shape). To use the Lasso tool, just drag and create a path surrounding the area to be selected. If you don’t return to the starting point to close the selection before you release the mouse button, Photoshop completes the path by finding the most direct route back to your starting point.
As with the Marquee tool, you can press the Shift key to add to a lasso selection and press the Alt (Windows) or Option (Mac) to delete from a lasso selection.
Hold down the Lasso tool to show the hidden Lasso tools:
Polygonal Lasso tool: Click a start point and then click and release from point to point until you come back to close the selection.
Magnetic Lasso tool: Click to create a starting point and then hover the cursor near an edge in your image. The Magnetic Lasso tool is magnetically attracted to edges; as you move the cursor near an edge, the Magnetic Lasso tool creates a selection along that edge. Click to manually set points in the selection; when you return to the starting point, click to close the selection.
You may find that the Polygonal Lasso and the Magnetic Lasso tools make less-than-ideal selections.