He refers to 'space-time', don't know if there is a difference or what it really means.
"Space time" is a term used to describe the proven relationship in the universe that exists between large distances, speed, location in the universe and time itself. They are linked.
Prior to the development of the general and special theories of relativity it was believed that time was constant no matter where you were in the universe... That is, it was always "now" at every location in the universe.
Einsteins theories (later experimentally proven), showed that time is "relative" meaning that time itself passes differently at any two different locations, this effect is dependant on differences in speed and or strength of gravitational effects between two given locations of the universe... His theories showed a relationship exists between speed, distance and time. Hence "space time"
Eg if you travel at a speed close to the speed of light time travels slower for you compared to another individual who is stationary. You've seen interstellar? This is real science.
Also see the twins paradox this will give you an idea.