Rising star is the lower of two professional categories, usually limited to couples who have not previously won the division at that competition (or had a certain placement in a championship, or related conditions like that).
The ideas has also been copied at a few amateur competitions, but it would be clearly called an amateur rising star event.
The chain studio systems (Murray's and Fred's) have their own house competitions which are closed to students and employees of that system, so generally less prestigious than the major open-to-all events, though of course there are open competitions which may have fewer entries in a given category.
It is not required to compete as an amateur before turning pro, but it is generally a good idea. Top amateur competitors often quickly rise in the pro ranks during their first year after making the switch, while it is comparatively unusual for those who began their career as professionals (typically as adult studio employees, vs as children or teenagers for the amateurs) to break out and achieve competitive fame.
Also worth mentioning that the studio system (and direct-to-pro career track) plays a larger role in the American Style events than in the Internal Style events, in part because the young adults coming out of intense youth amateur programs tend to stick to international style.
