RNTIs (Radio Network Temporary Identifiers) are used by the gNB scheduler to address UEs and identify different types of transmissions on the 5G NR air interface. The RNTI is embedded in the CRC of the DCI (Downlink Control Information) — the UE monitors PDCCH by attempting to decode DCI with its assigned RNTI. Only if the CRC matches does the UE process the message.