Cosmonaut is the Soviet/Russian term for astronaut. The strictest definition of either, since the words are synonymous, is a person trained by a spaceflight program to serve in a spacecraft. The cosmonaut can take a number of roles in space fights. They may command a mission, fly the spacecraft, or serve as a crewmember. With the growth of space tourism, distinction between cosmonaut and space tourist often needs to be made. People simply flying on a shuttle mission, who are there merely to travel, aren’t considered astronauts or cosmonauts.
The reason Americans are so familiar with the term cosmonaut is because of the Soviet/US Space Race, an effort of both countries during the Cold War to be the first in exploring space, landing on the moon, and making new discoveries about space travel. Initially the Soviet Program took an early lead. Cosmonaut Yuri Gagarin was the first man to orbit earth and reach space in 1961. That same year, the USSR scored another early victory when cosmonaut Gherman Titov spent over a day in space.
American astronauts, at least from the American perspective, “won” the race by being the first to land on and walk on the moon. However, many consider early Soviet victories to be equally important. For instance in 1963, Valentina Tereshkova, was the first woman in space. The US would not send a woman into space, Sally Ride, until 20 years later in 1983.
The early Soviet space program was marked by a considerable amount of secrecy, including cover-ups when people were killed or injured. They were more reckless, and some of the cosmonauts were viewed as more or less expendable. Victory in space and beating the US was powerful motivation, but it also prompted both the US and the USSR to be highly secret in their operations.
As the end of the Cold War dawned, it ushered in a new era that was much more cooperative. For the first time, the US and USSR worked together, shared at least some information, and even planned joint missions. Exploring space, as either cosmonaut or astronaut, and understanding the mechanism of space flight allowed for both countries to benefit significantly.
Speculation about early failures on the part of the US was largely answered when President Gorbachev declassified much of the information about the Soviet program. For the first time, the world learned about the deaths of cosmonauts who had not really been known, and about accidents. In communist Russia, admitting these defeats would have been tantamount to conceding failure in the Space Race.
Just like American astronauts, past and present cosmonauts are intelligent, extremely brave, and gifted. The modern cosmonaut tends to be associated with either the Russian Federal Space Agency or the National Space Agency of Ukraine. Emphasis in space travel is on learning more, sharing such information and hopefully benefiting the lives and careers of future cosmonauts.