NEODYMIUM "RARE EARTH" MAGNETS

Why do some stores call the silver magnets neodymium and others call them "rare earth"?

"Rare earth" is a common phrase for neodymium, so they are the same thing. Similar to how people call US currency a "dollar" or a "buck".

What is N55 and what does it mean regarding magnets?

N55 is the grade or strength.