Define Target Groups
It is recommended to group your visitors into target groups. They help you to keep track and have an overview about what content you need to provide and about which content is delivered to what visitor.
Thus, Target Groups are the core entities for personalizing content.
Target groups are defined centrally, have an unique name, can have a description and may be deactivated.
The threshold is needed in combination with visitor profiling. Based on the behavior, a visitor can get target groups assigned. Thus a visitor can belong to multiple target groups with a specific assignment count (= times a target group got assigned and represents a certain relevance). Once the assignment count passes the configured threshold, the visitor really belongs to the target groups and it is used for personalized content.
See visitor profiling for further information on profiling visitors and assigning target groups.