Extraterrestrial life is life originating outside of the Earth. It is the subject of astrobiology and its existence remains hypothetical, because there is no credible evidence of extraterrestrial life which has been generally accepted by the scientific community.
The Drake equation is a famous result in the speculative fields of exobiology and the search for extraterrestrial intelligence. It can be used to predicate (read as calculate) the number of advanced civilizations in our galaxy right now. But the result are not accurate and lots of criticism involved.
Disagreement (ie general ignorance) over these numbers leads to estimates of the number intelligent civilisations in our galaxy that range from 10^-5 to 10^6.
i. panspermia predicts 37964.97 advanced civilisations in our galaxy with a standard deviation of 20.
ii. the rare life hypothesis predicts 361.2 advanced civilisations with an SD of 2
iii. the tortoise and hare hypothesis predicts 31573.52 with an SD of 20.