A cluster is a SQL query that is an alternative to use if the criteria you need is too complex for the Criteria Editor. While the Criteria Editor is capable of building the audience based on a complex criteria, you many receive an error because it takes the system too long to get the counts. This is when a cluster is needed.
In the latest version of Criteria Editor, select Clusters to reveal the cluster filter.
In the older version of Criteria Editor, select Legacy to reveal the cluster filter.
Filters will only work on a cluster if the type of data specified in the filter is included in the cluster.
When excluding from a cluster or excluding a cluster from a Data Source, the Exclude by Email filter has been found to be the most efficient.