SpaceX made history by reflying a Falcon 9 rocket booster that delivered a payload into space last year. This rocket landed on a droneship and yesterday SpaceX flew it for the second time, which is a world first as nobody has ever re-used an orbital class booster.
The "flight proven" Falcon 9 booster performed perfectly and delivered the SES-10 communications satellite into geostationary transfer orbit. After performing its main mission, the Falcon 9 booster returned to Earth and landed succesfully on the Of Course I Still Love You droneship.
It took Elon Musk 15 years to reach this goal but now SpaceX has finally proven that it's possible to re-use rocket boosters, a feat many in the traditional space industry said was impossible. This is an important milestone because by being able to recover the most expensive part of a rocket launch, SpaceX hopes it can dramatically reduce the cost of space travel.
Musk envisions the future of the space industry as similar to what we see in the aviation market. Rather than demolishing a plane after every flight, it gets inspected and refueled, which is basically Musk's goal for space travel as it would lead to much lower costs.