An asteroid is sometimes called a minor planet or planetoid. They are small Solar System bodies in orbit around the Sun. There are tens of thousands of them grouped in the main asteroid belt between Mars and Jupiter. They are smaller than planets but larger than meteoroids, meaning that an asteroid can range from a few meters wide to hundreds of km wide. The term ”asteroid” has historically been applied primarily to bodies in the inner Solar System since the outer Solar System was poorly known when the term came into common usage. In general, they are rocky bodies that do not have an atmosphere, although some have a high metallic content. A few have their own moons.
A meteorite is any object that has entered the atmosphere of another object and survived to impact the surface. Another way to explain a meteorite is to say that they started out as little chunks of rock and debris in space called meteoroids. They become meteors when they fall through a planet’s atmosphere; leaving a bright trail as they are heated to incandescence by the friction of the atmosphere (shooting stars). Pieces that survive the journey and hit the ground are called meteorites. Occasionally, an object large enough to be considered an asteroid will enter an atmosphere. Its remnants are also called meteorites if they impact the surface.
To nail down the answer to ”what is the difference between asteroids and meteorites”, it is their location. An asteroid is always going to be in space. Once it enters an atmosphere it becomes a meteor, then a meteorite if it hits the ground. A meteorite is always going to be on the ground. Each is made of the same basic materials: metal and rock. Each originated in space. The main difference is where they are when they are being observed.
Meteorites are the source of a great deal of the knowledge that scientists have about the composition of other celestial bodies. Scientists have traced the origination of the meteorites found here on Earth to four other bodies: the Moon, Mars, the asteroid 4 Vesta, and the comet Wild 2. Be sure to check out those bodies as part of your research into asteroids and meteorites.