What does it mean when the compromise of 1850 allowed popular sovereignty to decide the slavery question

The Compromise of 1850 by Henry Clay gave Kansas and Nebraska the decision on letting the people vote for if it will be a slave state or a free state.

Explanation:

At first it was proposed that only states below the Missouri border would be considered slave states. That was established due to the Missouri Compromise. When more slave states were trying to be made, they started to go past that line. Soon they established that the Missouri Compromise as unconstitutional so they then gave new states the choice of being a slave state or free state (Popular sovereignty).