The Drake equation is a mathematical formula used to estimate the number of detectable extraterrestrial civilizations in our galaxy.
The equation was first proposed by astrophysicist Frank Drake in 1961 as a way to organize the various factors
that could influence the likelihood of the existence of extraterrestrial life.

It takes into account factors such as the rate of star formation, the fraction of stars with planets,
the fraction of planets that are in the habitable zone, the fraction of planets that develop life,
the fraction of planets that develop intelligent life, and the length of time that civilizations are able to communicate.

The formula is

N = R ⋅ fp ⋅ ne ⋅ fl ⋅ fi ⋅ fc ⋅ L

Where

N = the number of extraterrestrial civilizations in our galaxy with which communication might be possible
R = the average rate of star formation in our galaxy
fp = the fraction of those stars that have planets
ne = the number of planets per star that are in the "habitable zone" (where conditions are right for liquid water to exist)
fl = the fraction of those planets on which life develops
fi = the fraction of those planets on which intelligent life develops
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time such civilizations release detectable signals into space

The formula is not meant to be taken as a precise prediction, but rather as a way to organize our thinking about the factors
that could influence the likelihood of extraterrestrial life, and to help guide scientific observations.
The values for the various factors in the equation are uncertain and subject to ongoing research and debate.