Paths provide smooth outlines that you can convert into precise selection borders. You can also convert selection borders into paths, using the Direct Selection tool 
for fine-tuning.
You can define any closed path as a selection border. A closed path can be added to, subtracted from, or combined with the current selection.
at the bottom of the Paths panel.-
Feather Radius
Defines how far inside and outside the selection border the feather edge extends. Enter a value in pixels.
Anti-aliased
Creates a finer transition between the pixels in the selection and the surrounding pixels. Make sure the Feather Radius is set to 0.
For more information on these options, see Soften the edges of selections.
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Any selection made with a selection tool can be defined as a path. The Make Work Path command eliminates any feathering applied to the selection. It can also alter the shape of the selection, depending on the complexity of the path and the tolerance value you choose in the Make Work Path dialog box.
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Click the Make Work Path button
at
the bottom of the Paths panel to use the current tolerance setting,
without opening the Make Work Path dialog box.Alt-click (Windows) or Option-click (Mac OS) the Make Work Path button at the bottom of the Paths panel.
Choose Make Work Path from the Paths panel menu.
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Tolerance values can range from 0.5 to 10 pixels and determine how sensitive the Make Work Path command is to slight changes in the selection shape. The higher the tolerance value, the fewer the anchor points used to draw the path and the smoother the path. If the path is used as a clipping path and you have problems printing the image, use a higher tolerance value. (See Print image clipping paths.)
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