Here's what happens:
* The team discovers a hidden message in the Stargate's control room.
* The message reveals that the 9th chevron doesn't just open a gate to another location; it activates the "Destiny" program, which is a powerful energy source that could potentially destroy the universe.
* The team initially believes this program is designed to destroy the universe, but they later learn it can also be used to "heal" the universe, effectively fixing the damage caused by the Ancients' previous overuse of the energy source.
It's a significant moment in the series, as it reveals the true purpose of the Destiny program and the potential dangers and rewards associated with it.