This concept can be summed up easily; space and time are connected. But what does this mean? For example, a day is 24 hours, but it is also 24,894 miles or the amount of distance the Earth rotates. The Universe is so immense that distance is measured in terms of light years. A light year is the distance that light travels in a year. Light moves at approximately 186,000 miles per second, which translates to roughly 6 trillion miles. So when your traveling in space, you can measure your journey in both distance and time travelled.
The relationship runs even deeper. When travelling in space, the faster you move, the slower time moves. The fastest thing in the Universe is light and the closer you move toward its speed, the slower time goes. For example, if identical twins were separated; Bob stays on Earth, and Ed experiences a space mission at the speed of light. If they are 20 when the mission starts, on Earth the time elapsed is 22 years. When the twins are reunited, Bob will be 42, however Ed will only be 30.