The circuit shown is used for finding the difference of two voltages each multiplied by some constant (determined by the resistors). 

"The name "differential amplifier" should not be confused with the "differentiator", also shown on this page."


"The "instrumentation amplifier", which is also shown on this page, is another form of differential amplifier that also provides high input impedance."

Difference amplifier
Amplified difference
शून्य स्तर अनुसूचक (Zero level detector)
डिफरेंशियल एम्प्लिफायर (Differential amplifier)