Laika was a stray, living on the streets of Moscow in the 1950’s, when she was chosen for a special task—Laika was to be the sole occupant of the Sputnik 2 spacecraft, to be launched into orbit in late 1957.
There was little known about what impact spaceflight would have on living creatures at the time, and so, before a human could be sent with into space with reasonable assurance of safety, testing on animals was seen as necessary, and on November 3, 1957, Laika was sent into orbit via Sputnik 2.
Laika did not survive the mission. In fact, Sputnik 2 was not built for re-entry. Those who had sent her into space knew she would not return, regardless of what happened.
Initially, it was reported that Laika had died some 6 days into her mission from lack of oxygen, but in 2002, the truth was made public—Laika had died from overheating, only hours after launch. She was approximately 3 years old.