A typical space flight profile:
After air launch, the unmanned launcher fires its first stage engine, and climbs away. After gaining much altitude, the first stage burns out at about 150 km, and is released. The second stage then fires, building up speed to orbital velocity (about 7.8 km/s), and the last bit of altitude to orbit, at about 250-300 km altitude.
When orbit is reached, the payload, a nano- or microlight satellite, is released. The payload is now in orbit! And there it can begin its mission. Meanwhile, the second stage performs a brief and small de-orbit burn with the last bits
of propellant that are left in the tanks. After a few orbits, this stage reenters the Earth’s atmosphere, leaving no space junk behind.
After the air launch, the carrier aircraft has flown back to the airport. There it will be prepared for another flight!