In case you have not heard Philae landed on Comet 67P/Churyumov–Gerasimenko on November 12th 2014. Although it has been the first spacecraft to ever land on a comet and has been considered mission success but the landing was not as smooth as expected.
Lets start with the plan for the landing before we talk about the actual landing. The plan for Philae was to separate from Rosetta and fall to the surface of the comet. Philae was not designed to steer or control its direction in any way but instead the angle and speed of its separation was to determine the landing site. After separation from Rosetta Philae was planned to reach the surface and have a thruster push itself into the surface of the comet allowing the foot screws to begin screwing into the surface of the comet. To make sure the Philae was secure it was going to launch a harpoon into the surface of the comet. With all three of these Philae was planned to be to be secured on the surface of the comet in the sunlight so that it can run its various tests.
What actually happened is much different. Philae before separation went through many checks to make sure that everything was ready for landing. During these checks the team found out that the thruster system was not working anymore so it would not be capable of firing the thruster to push Philae downwards towards the comets surface. The team decided to still continue with the landing considering that Philae still had its foot screws and harpoon system. Philae separated from Rosetta perfectly and fell to the surface of the comet. Philae sent back signals that it landed on the surface and everybody was excited but maybe a little to soon. Shortly afterwards it was realized that Philae was not actually secured on the surface the way they planned. Philae actually bounced after first impact took roughly an hour to come back down and bounced again before it finally made its final landing a few minutes later.
After recieving some data it was determined that the Harpoon system failed to fire which is why Philae bounced. Philae ended up in a shadow of a cliff which meant that it was not capable of getting any solar energy and had to run off of what battery life it had.
Before the batteries depleted Philae was capable of successfully sending back science data and communication data to accomplish the mission. Philae was also capable of moving and rotating slightly to hopefully receive more solar energy later for a possible chance of coming out of hibernation.
Philae will be in hibernation as long as it does not get enough solar energy to wake back up. The hope is that as Comet 67P gets closer to the sun that maybe there will be a chance for Philae to have a better angle towards the sun and be able to receive enough energy to wake up.
For now humans can now say that they successfully landed a spacecraft on a Comet which has never been stated before!