The Basics 
This tool lets you extract foreground from the active layer, using the SIOX method. To create a selection, set roughly foreground you want to extract. Select as little of the background as possible. As soon as you're finished (the selection is closed) the rest of the image goes dark. Now draw the line through the foreground, going through all colours that will be used for extraction. Then after releasing the mouse-button, only the actual foreground is selected. Remember to press Enter after finishing the selection, or you could actually loose it.
- Modes - determines the way of creating the selection, whether it'll be combined with existing one and such
- Antialiasing - causes the boundary of the selection to be drawn smoother
- Feather edge - causes the boundary of the selection to be blurred
- Contiguous - if this option is enabled, only area contiguous to the stroke is selected
- Interactive refinement - settings for the brush
- Smoothing - controls the smoothness of selection
- Preview colour - colour of the selection background
- Colour Sensitivity - set the sensibility for colours of the selection
Modes, Antialiasing and Feather Edges 
- See Selection Tools#Modes for information about Modes
- See Selection Tools#Antialiasing for information Antialiasing
- See Selection Tools#Feather Edges for information about Feather Edges option
When this option is enabled, only areas contiguous to the stroke will be selected. When this option is not enabled, all areas of the same colour in the rough selection will be selected.
Interactive refinement 
The following options are for controlling the brush of foreground select tool.
Mark foreground/background 
Whether foreground or background colour will be used for the stroke. Ctrl is used to toggle between those. Remember! background colour is used for erasing.
Small/Large brush 
This slider lets you adapt the size of the brush. Small brush is good for details, while large is good for general foreground selection.
This slider lets you to remove holes in the selection. Also remember - smaller values may create a better border but include these holes in the selection.
Preview colour 
Selected colour will be used to mask the image background. Possible options: red, green, blue.
Colour sensitivity 
This option uses L*a*b colour model. If your image contains many pixels of the same color in different tones, you can increase the sensibility of the selection for this colour.