Unlike most meteors, NEOs can be quite big and would do a lot of damage if they were to collide with Earth. The 1.6 km wide Baringer crater (shown right) was created by a meteor that was just 40 metres across.
It is possible that a large NEO may actually hit the Earth at some time in the future. Although this is very unlikely to happen in our lifetime, astronomers are trying very hard to find and track as many NEOs as possible in order to see if they might be a danger to us in the future.
To learn more about the chances of a large NEO impacting Earth, click here.
If astronomers can find big Earth-threatening NEOs early enough, it should be possible to "push" them out of the way and stop them crashing into us. However, any that do get through could have devastating results.