just resuming there are a lot of terms you will find in learning snmp.
as mibs, agent, nms, .....
but resuming, it is a protocol for network monitoring and management.
it works int a client /server role, where with the help of snmp minitoring software installed in the server device, you can monitor network status about all devices and conditions of an entire network, you can also configure remote devices, by snmp (not recommended), and also send traps borking the defined threshold to the nms device, insted of it to send a get responde from the agent devices (the monitored one).
resuming it is like a domain where all devices must belong the same adminstrative domain (commmunity), you can also send encrypted monitoring communication wiht new versions of snmp.