Maybe if you do a bit of searching here and there then you could understand what happened but in summary, there are some two Astronauts that have been stuck in the International Space Station since last year. The reason for this was that the spacecraft with which they were supposed to use for returning to earth faced some propulsion problems, so NASA decided to avoid risking their lives and returned the spacecraft without the crew.
SpaceX is said to be making preparations for their return soon.