Q: Why do I need to store my eggs large end up?
A: Storing your eggs large end up will keep them freshest. This is because the air cell in an egg is located at the large end, so less moisture will evaporate out of the egg if it is set with the air cell up in the carton. The pointy end, with egg white closer to the porous surface of the shell, is less exposed to air when it is pointing DOWN in the carton. Frankly, though, if you are storing eggs for eating, it probably won't make much difference unless you are storing them for very long periods of time (and we hope you're eating them fresh!).
If you are storing eggs for hatching, on the other hand, keeping them large end up is much more important.
When storing eggs for hatching, you'll want to store the egg large end up is so the air cell does not misplace, which can cause a reduction in hatchability. Also--don't put eggs you mean to hatch in the refrigerator! Store eggs for hatching, ideally, at a temperature of 60 degrees Fahrenheit or so.