What's the difference between meteoroids, meteorites, and meteors?

You're talking about a grain of sand or a stone or a rock that's drifting in space, and then the Earth happens to get in the way, so the stone falls down to Earth, and it makes a bright streak of light while it's falling through the atmosphere and burning up from the friction.

-- While it's drifting in space, it's a meteoroid.

-- While it's falling through the atmosphere burning up and making a bright streak of light, it's a meteor.

-- If it doesn't completely burn up and there's some of it left to fall on the ground, then the leftover piece on the ground is a meteorite.