DMVPN Configuration commands

Hi @Network_Eric
“ip nhrp nhs {nhs_ip_in_overlay_net}” ← what does that do?
"ip nhrp nhs {nhs_ip_in_underlay_net} nbma {nhs_ip_in_overlay_net} ← what does that do?
"ip nhrp nhs {nhs_ip_in_underlay_net} nbma {nhs_ip_in_overlay_net} multicast ← what does that do?

“ip nhrp map {overlay_ip} {underlay_ip}” ← what does that do?
“ip nhrp map multicast dynamic” ← what does that do?
“ip nhrp map multicast {underlay_ip}” ← what does that do?

im totally totally lost and i need your help. im not understanding the difference between all these commands at all