The Alien setting has FTL travel of varying speedsFTL travel of varying speeds. People who travel on long journeys in slow ships travel in stasis, also known as cryosleep or hypersleep. These are the pods you see people enter or exit near the beginning or end of most of the films.
The point of stasis is to reduce the consumption of resources and slow down aging. Effectively, people who do a lot of deep space travel have a biological age significantly lower than their chronological age.