Hi,
similar questions have been asked so often that there is a sticky for this:
Dual or single supplies for opamps.
hope that explains enough for you.
What people mean when they use the term 'virtual ground' in this context is using an equally matched series of two resistors between V+ and V-. This is not really what virtual ground means, however, this voltage divider will divide the source voltage in half, so if you use the tap between the resistors as your ground, then V+ is at one half the source voltage, and V- is negative one half the source voltage.
You may want to google voltage divider.
regards