This is the user that can be associated with a particular SNMP group. To create an SNMP user:

Router(config)#snmp-server user <username> <Group name> v3 auth <sha|md5> <authentication password> priv <encryption algorithm> <encryption key>

For example:

Router(config)#snmp-server user MICHAEL CISCO1 v3 auth sha cisco123 priv des56 secret123

Here, MICHAEL refers to the username and the user is mapped to a group called CISCO1. So basically, the user can access a view that is associated with this group. Also we can see that the password used here is cisco123 and the encryption key is secret123.