The bit on the left of the vertical bar is what gets displayed to the user while the bit on the right is the actual filter used by the dialogue. You often do but you don't have to include the filter in what gets displayed to the user.

The filters always come in pairs like that. If you want a choice of two filters you would have four sections separated by vertical bars. The first and third would what got displayed to the user while the second and fourth would be the actual filters.

Try setting this as the filetr for a dialogue:
Code:
Image Files|*.gif; *.jpg; *.png; *.bmp|All Files|*.*
and then try this:
Code:
Image Files (*.gif, *.jpg, *.png, *.bmp)|*.gif; *.jpg; *.png; *.bmp|All Files|*.*
Notice that the functionality of the dialogue doesn't change. Only what the user sees changes, because you've added the extra bit to the string displayed to the user.