Discontinuous Reception is used to reduce battery consumption at UE because UE does not receive data all the time from eNodeB.
Continuously monitoring PDCCH results more battery consumption. UE goes to sleep mode for certain period of time and wakes up for certain period of time using DRX mechanism to save battery life. However based on different type of scenarios different parameters have been defined and out of those parameters two parameters "DRX inactivity timer" and "DRX re-transmit timer" are in question,
DRX inactivity timer is the number of sub-frames in which UE will be in "ON"/"Active" state. In other words for how long DRX is disabled for an UE
DRX re-transmit timer is the number of sub-frames in which UE is expecting re-transmission from eNodeB. It is just used to extend the DRX active mode by configured number of sub-frames.