The universe is all of space and time and thier contents, including plannets, stars, galaxies and other forms of matter and energy. First we have our sun, around which all the plannets including Earth revolve. There are moons, billions of stars, asteroids and commets and all this constitues a Solar System. This solar system is a part of the Milky way galaxy which is one of billions of other galaxies which constitues the universe. The universe is everything that is existing, existed or will exist. It's size is unknown but to where it is observed, it is 93 billion light years in diameter.
A black hole is a large amount of matter squeezed into a very small area due to which its is extremely dense and exhibits a very strong gravitational force. This gravitational force is so strong that anything, even light, is pulled inside it. If a humangus star dies and the core left behind has a mass three times more than the Sun, then it becomes a black hole. The force of gravity then shown is extremely strong. If any celestrial body or matter comes close to it, it will be pulled in by the black hole. It has the power to even pull the sun inside it if it comes closer.
A wormhole is a speculative structure linking disparate points in spacetime. It is basically a tunnel with two ends at different points in spacetime. For better understanding, take a rectangular sheet of paper and make two circles at the two opposite sides( breaths of rectangle) and mark them A and B. Now draw a line betweem them. This line potrays the path you have to follow to get from A to B. Now fold the papaer along this line. You will see after folding, points A and B overlap. This is what a wormhole does. It bends spacetime to create a small pathway between two very far points. Therefore it makes distance between two very far away points very small.
When you look between two planets or any two celestrial bodies, what do you see? What is mist of the universe filled with. Its empty space. There is empty space everywhere in the universe. Most of this universe is empty space. Scientists believe that there is a possibility if having a different kind of matter in those spaces who's particles are yet not discovered. They believe this due to some unexplainable observations like various gravitational effects that do not match the conventional gravity theories or the fact that our universe is expanding at an increasing rate for unknown reasons. These things could be explained if there was some large amount of undetected matter that existed. Dark matter is called dark because it does not interact with light thus making it invisible and hard for us to detect.many believe this dark matter could be responsible for the ghostly activities that occur in this world.
Time dilation is the difference in time recorded or time elapsed by two different observers due to velovity difference or different locations relative to gravitational fields. There were two twin brothers, one of which was send to space in a rocket with a clock. After his returning and reuniting with his other twin, time was measured. The twin who went in space on a rocket had aged less than the twin on stayed on earth. Time had elapsed slower for the first twin. There have been differences found in time on space shuttles and satellites compared to earth. This occurrences are a result of time dilation. So one person can go into the future by spending some time out in the space traveling at the speed of light, when he comes back, more time than he was gone for would have elapsed on earth.