Outer space starts at 100 km altitude (Karman line) where the atmosphere is so thin that it’s no longer provide aerodynamic lift and objects need to travel faster than orbital velocity to support itself.
Low Earth Orbit (LEO) starts around 160 km and up to 2,000 km. Below 160 km atmospheric drag is so strong that objects are quickly losing speed, so orbit is rapidly decaying.
To stay long enough on LEO without decaying objects needs to use some propulsion to boost their speed periodically. For example, ISS reboosting itself a couple of times per year.
Delta-v requirements to reach Low Earth Orbits starts approximately at 9.4 km/s.