When a Inverting Opamp Configuration is at a steady state, we say the Inverting Input is at a Virtual Ground. That means it is at 0V w.r.t to the dual power supply ground, but it cannot drive or draw any current. It is at a high impedance, but still at 0V. When you buffer this 0 V, you get a low signal ground for a opamp supply.
Analog Buffer and Inverter Switching with logic - del20016
This gnd. can sink and source in a couple of mA. You can use it with low power opamp circuits for portable battery operated devices. This creates a virtual +/- 6 V dual supply from a 12V battery. This may be needed in cases where some instrumentation opamps need the negative supply or your design demands a measurement around zero.
You may get a more loadable ground using a Power Opamp, i have not tried. The above circuit gnd cannot be used as a return path for LED's or Relays. You can drive these, between VCC-VDD, but translate levels to drive them.
Essentially a high-gain dc amplifier, with a high input and low output impedance, the modern op-amp has a multitude of practical applications both in the home and in industry. This handbook, which should prove valuable to the electronics hobbyist, student, and engineer alike, first outlines the essential characteristics of the op-amp, and then presents 110 highly useful projects -- ranging from simple amplifiers to sophisticated instrumentation circuits.