RSRP (Reference Signal Receive Power) is the average power of Resource Elements (RE) that carry cell specific Reference Signals (RS) over the entire bandwidth, so RSRP is only measured in the symbols carrying RS.
* RSRP is the average received power of a single RS resource element.
* UE measures the power of multiple resource elements used to transfer the reference signal but then takes an average of them rather than summing them.
* Reporting range -44…-140 dBm
As Alkesh pointed out this is used in cell reselection
SINR (Signal to Interference & Noise Ratio) is a measure of signal quality as well but it is not defined in the 3GPP specs but defined by the UE vendor.
It is not reported to the network. SINR is used a lot by operators, and the LTE industry in general, as it better quantifies the relationship between RF conditions and Throughput. UEs typically use SINR to calculate the CQI (Channel Quality Indicator) they report to the network.
Relation between SINR and RSRQ