Diploid/Haploid number confusion?

In mitosis and meiosis, the terms of 2n=4 and n=2 are commonly used. I know that for mitosis, 2n=4 remains constant throughout while for meiosis, 2n=4 becomes n=2 as it is reductive cell division. However, I don't really understand what the "n" means, or how it is related to the chromosome number?? Can someone enlighten me?