First contact is a term used to describe a first meeting of two previously unknown cultures.
In science fiction
First contact is a common science-fictional theme about the first meeting between humans and aliens.
There have been entire series devoted to this theme. One classic series is the "interstellar trader" series by Andre Norton. A more modern treatment, using radio rather than spaceships, is Contact by Carl Sagan. As another example, in the fictional Star Trek universe, official first contact for humans occurs on April 5, 2063 (see Star Trek: First Contact). The novel The Gods Themselves by Isaac Asimov and films Alien and ET are good examples of First Contact stories.
Since the best evidence suggests that there has never been contact between humans and extraterrestrial species, the degree of culture shock which might occur is highly speculative. Often in science fiction, the clash between intelligent species has resulted in warfare, but some science fiction writers, such as Arthur C. Clarke, have suggested that the technological gulf that would exist between two intelligent species would be so vast that Star Wars style scenarios are highly unlikely. Consider for example, how soldiers from the 16th century would fare against 21st century weaponry. Magnify the technological gap by thousands or even millions of years of additional development which may have occurred in an extraterrestrial species, and it becomes clear that the differences could potentially be so large as to make warfare absurd, and even understanding impossible. Pure statistical chance suggests that it is unlikely that two civilizations would be at the same state of technological development. In the third of his Clarke's three laws, Clarke stated "Any sufficiently advanced technology is indistinguishable from magic."
The theme of first contact is not limited to science fiction. For example, many stories about the old American West featured a first contact between European colonists and Native Americans. (In fact, early Star Trek episodes seem to have been modeled after westerns.)
It is clear from the historical record here on Earth between societies of the same species, that the disruptive nature of first contact generally favors the more technologically advanced side, with often dire consequences for the less advanced side. It is nearly impossible to predict what the first interactions between two different intelligent species might be. Beyond the language barrier, physical differences might make a common basis for shared experience impossible, or perhaps even repugnant.