Select Menu

Select All
Selects the whole layer.
Deselect
Deselects everything(except for active Selection Mask)
Reselect
Reselects the previously deselected selection.
Invert Selection
Inverts the selection.
Convert raster selection to vector selection.
Convert Shapes to Vector Selection
Convert vector shape to vector selection
Convert to shape
Converts vector selection to vector shape.
Display Selection
Display the selection. If turned off selections will be invisible.
Show Global Selection Mask.
Shows the global selection as a selection mask in the layers docker. This is necessary to be able to select it for painting on.
Scale
Scale the selection
Select from Colour Range
Select from a certain color range.
Select Opaque
Select all opaque(non-transparent) pixels in the current active layer. If there’s already a selection, this will add the new selection to the old one, allowing you to select the opaque pixels of multiple layers into one selection. Semi-transparent(or semi-opaque) pixels will be semi-selected.
Feather Selection
Feathering in design means to soften sharp borders. So this adds a soft border to the existing selection.
Grow Selection
Make the selection a few pixels bigger.
Shrink Selection
Make the selection a few pixels smaller.
Border Selection
Take the current selection and remove the insides so you only have a border selected.
Smooth
Make the selection a little smoother. This removes jiggle.