The Pooled Sessions View is for those servers with Pooled Sessions licensed. This is not a very common situation but can be useful when pooled sessions are configured.
The View is selected by right-clicking on the Cluster node and selecting Pooled Sessions View:
The view is like the Sessions and Users View with the same actions available on each server, and the meanings of the columns like those described in the Sessions View:
As our example server has no pooled sessions, all the numbers in this screen clip are zero, but in a real configuration they would have the pooled session numbers: