Once a session is started, assessment results will become available under "Discovered Server List" section:
Server
The URL being assessed by N-Stalker Web Discovery.
Banner Type
What is the reported server banner (a string that web servers usually provide in all HTTP communications).
Discovered Type
This is a guess on what is the real technology behind that web server. Sometimes servers might provide an incorrect banner or nothing at all to avoid leaking details of its underlying technology.
N-Stalker will run a series of tests to identify certain behaviors and common patterns that indicate a particular server type.