I know that it works as an amplifier in the transition or linear region. But how? What is the exact working operation? Please also explain in terms of i/o voltage/current?
I take it you have a homework problem that is asking you to explain how a CMOS inverter can be used as an oscillator and wants you to explain it in terms of I/O voltage and current?
You need to show YOUR attempt to answer YOUR homework problems. We can then use that as the starting point for guiding you through any misconceptions.