If output impedance of a point is a high value then connecting another circuit at that point will load it resulting in malfunction or error. Buffers are used as interface between circuits. Low impedance of an output means it can source sink lot of current, when you need 2 opamps use LF353 or TL072 which are dual opamps.
Buffer or Unity Gain Op-Amp
When no gain is required and you need to match impedance this can be use. Front end amps, Sensor amps. Polarity Inversion in Analog Computing or Signal Conditioning.
This has Virtual Meters and Pots, shows how a Operational Amplifier works. Slide the Potentiometers and vary the mV Source, See Output DVM. Slide the Potentiometers just like you would operate a Sliding Control. Drag the Knob on Pot to increase or decrease the resistance. The Resistance is shown is blue letters and dynamically alters value as you slide the pot. The mV Source is varied by just moving or hovering mouse pointer over the two buttons, no clicking. The mV buttons are special, the variation picks up speed if you let the mouse pointer remain on the button. This is Ramp-up and Ramp-down. This enables you to set it faster with just two buttons.
A non-inv FET input is the best buffer, for inverting buffer use high R values Using very high R values like 2.2M or higher requires a glass epoxy PCB and guard rings around pin 2, 3 to prevent leakage currents on the PCB reaching the PINs
Vout = -(Vin) for inverting
Vout = Vin for non-inverting
Also moisture and dust has to be prevented by using RTV coating or Varnish. Use 78L05 79L05 for the dual supply required by this circuit.
More at Analog Op-Amp Circuits