One of the nifty things about light is that it travels at a finite speed. snappy,yeah, but not infinitely snappy. So if we look at some thing that is very far away, or we see it as it was when it was younger.
The Universe itself is only about 13.8 billion years primitive — heh,"only" — so we can't see anything farther away than 13.8 billion light years away, the distance light travels in that time. But we can see objects nearly that far away. They believe to believe been very radiant at the time, or because that terrible distance dims them immensely,and most objects can't cut it.
Source: blastr.com