We do not yet know whether there is intelligence beyond Earth. The estimates of our chances to find extraterrestrials vary widely, from the claims that Earth is the only inhabited planet to the expectations of finding life near most starts. Just in case we unexpectedly run into sentient aliens, scientists have developed a langauage (hopefully) suitable for the first contact, called Lincos, which stands for the Latin phrase lingua cosmica.
The creator of the Lincos language is Hans Feudenthal, who described it in his book Lincos: Design of a Language for Cosmic Intercourse, Part 1, published in 1960; there is no Part 2, as he never got around to writing the continuation. Lincos is based on a combination of mathematical notation with simple constructs from natural languages. You may find examples of Lincos sentences in the related Wikipedia article. The purpose behind its design was to make it understandable to beings unfamiliar with human languages, who may have completely different communication mechanisms. Researchers later used similar ideas in CosmicOS, which is an "executable" message to extraterrestrials, to be deciphered and run as a program on their alien computers. Both Lincos and CosmicOS were mostly designed for radio transmissions, but so far they have not been used in any actual transmission.