CSI-RS Classification and Role - 5G NR

Channel-State Information -Reference Signal channel state information, is very important for improving the overall performance of the wireless system. After obtaining the CSI information, the base station can schedule MCS according to the channel quality, RB resource allocation, beam assignment to improve the rate, multi-user multiplexing MU MIMO, etc.

Nice Article Here 

https://forum.huawei.com/enterprise/en/introduction-to-5g-5g-nr-system-csi-rs-signal/thread/733957-100305

5G- Beam forming, Beam Steering, and MIMO - simplified.

Due to the high propagation loss of the millimeter wavelengths (mmWaves) employed in 5G new radio (5G NR) systems, plus the high bandwidth demands of users, beamforming techniques and massive Multiple Input and Multiple Output (MIMO) are critical for increasing spectral efficiencies and  providing cost-effective, reliable coverage.

Read in Full 

https://www.metaswitch.com/knowledge-center/reference/what-is-beamforming-beam-steering-and-beam-switching-with-massive-mimo