Right now, the Senate Majority Leader has complete control over the Senate's agenda. This means that one single person has the ability to (for example) prevent Presidential judicial nominees from even being considered by the Senate. For centuries, this system worked reasonably well because senators followed the norm of being willing to hear the nominations of a President from the opposing party, but recently, it's been demonstrated that we can no longer rely on that norm.
The proposal at hand is for a Senate rule (which the Senate itself would have to vote to adopt) that the Senate Majority Leader would no longer control what items can be put on the agenda. Instead, each sitting senator would, in turn, be able to add one item to the legislative agenda. This would give proportional representation to what's on the agenda to each party, preventing one party from blocking important business. The majority party could of course still vote against items they don't like, but this would mean that those votes would be public record. Currently, only the Majority Leader has to take heat for blocking judicial nominees, while other senators in his party can shrug and say it's not their fault: "I would have voted for that judge, but it never came to a vote." If the Majority Leader is in a safe state, being obstructionist does not hurt his reelection chances, and other senators of his party suffer no reelection damage.
This would reduce the power of the majority party in the Senate, but clearly the current system is flawed and needs to be adjusted.