Nowadays you can create Permanent, Transient or Segment audiences with Convert Experiences.
This type of audience is checked only at visitor bucketing time and not checked again. If the audience conditions are met by the visitor, the experience will run. If the audience conditions are not met anymore by the visitor on subsequent visits, it will not cause the experience to be stopped for that visitor.
For example, if you define an audience on specific hour and minute, e.g. hour 12 and minute 5, and while you visit the page the hour is 12 and minute is 3, the permanent audience conditions will not be matched and the experiment will be skipped (screenshot was taken from Google Chrome console while Convert Experiences debugger is ON):
If the permanent audience conditions were matched, then the experiment will be deciding which variation to present to you:
Then after few minutes if you try again, and since audience conditions were checked previously for you and a variation was served, the variation will still be served for you, even though you are outside the correct minutes.
With this audience type, audience conditions will be re-checked each time an experience is to be presented as opposed to the Permanent ones that will only be checked at visitor bucketing time.
For example, if you define an audience on specific hour, e.g. 9, and while you visit the page the hour is 11, the transient audience conditions will not be matched and the experiment will be skipped:
If you define an audience for specific hour, e.g. 11, and while you visit the page the hour is 11, the transient audience conditions will be matched and the experiment will be running:
If you open now another tab, while the experiment has already decided to serve you a variation, transient audience conditions will be checked again and if matched will serve you the same variation that was presented before:
Then if you visit again in next hour and transient audience conditions do not match, experiment is skipped.
Segments are a group of visitors that qualify for some Audience conditions (such as location, device used to access the site, hour of the day, and any other user behaviors) and can be used at a later time for targeting. Visitors in a specific segment are likely to behave or purchase in the same way. Thus, you can create segments by defining audience conditions that allow Convert Experiences to determine which segment a visitor qualifies for and run the appropriate variation.
A segment basically allows a visitor to qualify for an audience on subsequent visits even if they do not meet the audience conditions. That is why we call segments persistent. This means that if a visitor qualifies for such an audience in the first visit, he will continue to qualify for that audience every time he visits the page. If he visited multiple times, sometimes meeting the conditions and sometimes not, he will keep seeing the experiment.
Not attached to any experiment
You can also create an Audience that you would signal as a segment and not attach to any experiment. Users which match the audience it will be put on this segment, even if this audience has not been added to any experience. Later on, you can use this segment in an experience, and use already bucketed visitors on to it.
Segments are evaluated at the project level, so any visitor that reaches a page with the project tracking code and matches the Audience conditions designated as a Segment will be added to it.
Saved segments of a project can be used on other experiments as well.
Find here more details about segments.