Hi Rakesh, I don't have depth knowledge in Power Saving Mode (PSM) but would like to share my learning so far in this area.
When UE moves from connected to idle mode, it stars T3324 and UE remains reachable through paging from network side but after expiry of T3324, UE goes into power saving mode. In power saving mode, however UE can't be reach through paging but UE can initiate data transmission since UE is already registered with network.