(object orbiting the Sun that passes close to Earth)
A near-Earth object (NEO or if specifically an asteroid,
near-Earth asteroid or NEA) is an object, such as
a comet or asteroid, in solar orbit that passes near Earth.
An Earth-crossing asteroid (ECA) is an asteroid whose orbital
path crosses that of Earth.
A fast moving object (FMO) is an observed astronomical object
that appears to be moving very fast, which suggests it might be an
NEO because an object's movement appears fast if the object is nearby.
All these are of particular interest due to the potential for
a future impact with Earth
(those most likely are termed potentially hazardous objects,
PHOs, or if specifically asteroids,
potentially hazardous asteroids, PHAs),
and there have been a number of past and present surveys
to identify such objects:
Near-Earth objects are also useful destinations for space
probes, such as OSIRIS-REx visiting 101955 Bennu.
Comets and asteroids passing close to Earth are among
the easiest to reach.
NEOs are also classified based upon the relationship between their
orbits with that of Earth, each type referred to by the
name of the first such asteroid discovered:
Aten - ECA with semi-major axis smaller than Earth's and aphelion large enough to cross Earth's orbit.
Apollo - ECA with semi-major axis larger than Earth's and perihelion small enough to cross Earth's orbit.
Amor - passes close to Earth's orbit from the outside but does not cross it.
Atira or Apohele or IEO (for inner-Earth object) passes close to Earth's orbit from the inside but does not cross it.
The independent term Arjuna has been coined for any of these
with orbits much like Earth's.