The Fermi Paradox is the apparent contradiction between the high probability extraterrestrial civilizations' existence and the lack of contact with such civilizations.
There are billions of stars in the galaxy that are similar to our sun.
With high probability, some of these stars will have earth-like planets and some might develop intelligent life.
Some of these civilizations might develop interstellar travel.
According to this line of reasoning, our planet should have already been visited by aliens ...