A user segment represents a group of people in your target audience. You create segments by defining rules that include or exclude users according to their profile properties. For example, you could create a segment called High Earners that includes female college graduates earning more than $150,000 per year but excludes people from California. The rules that define this segment might look something like this:

Include these people:
   people whose Gender is Female
   and whose educationLevel is College Graduate
   and whose annualIncome is greater than 150000.00
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Exclude these people:
   people whose Home address's State is California

Once you set up this segment, you can use the Targeters window to create targeting rules for delivering personalized content to people who match the High Earners criteria. For example:

Show this content:
   newLuxuryCars
To these people:
   people in group HighEarners

As you can see, segmenting your target audiences can simplify your targeting rules and make them easier to maintain.