Voltage stabilizer just provides the stable or constant voltage as output in case of fluctuating input voltage. suppose if a T.V requires 120v ac but if the input voltage is varying between 220v to 240 v , then off course the T.V required input voltage may also vary around 115 to 125 v ac . This leads to burn out few sensitive electronic components hence by using a voltage stabilizer we can provide a constant voltage of exactly required 120v ac besides changing in the input voltage(i.e 220 to 240v ac).
u.p.s stands for un-interrupt power supply . That is the device which provides the back up( provides o/p in the absence of input) to prevent the sudden power shut down which comes into account.
example- a computer etc.
so what i say is the voltage stabilizer is different from a U.P.S, hence it should not be used in place of ups, which fails to give back up to the computer and finally turns off the computer in case of any sudden power cut , which leads to abnormal shut down of a computer