SNMP Server ? why do I need it ?

I have a raid 5 server running NT4.0 service pack 5. I recently lost a h.d. and swapped it out with a new replacement.

I was asked by my server support person where we bought the server to load there Global Array Manager s.w. which will help better manage my raid 5.

I downloaded the s.w. and when I tried to install, the install wants me to install snmp service.

What is snmp service ? what is it for ? what are the installation steps involved ?

Do I need to back snmp a certain way ?
My server support did not have a good answer.