The link I have provided for you has a really good explanation in it about the difference between reductional division, which is what happens in meiosis I, and equational division, which occurs in meiosis II.  I shall try to explain further here.

The purpose of meiosis is to take the genetic material contained in a nucleus and distribute it evenly into four daughter sex cells.  In meiosis I, the chromosomes are replicated, as they are in mitosis, separated into opposite ends of the nucleus, and form two daughter cells, each having 46 chromatids, which is half a chromosome.  That is why this division is called a "reductional division", because it divides the diploid number of chromosomes into a haploid number, with only half the normal count.  In humans, this would be 46 chromatids in each daughter cell.

In meiosis II, there is no replication of the existing 46 chromatids.  The chromatids separate again, half going to opposite ends of the nucleus, the nucleus separates into two nuclei, providing 4 daughter cells, each having 23 chromatids.  That is why this division is called an "equational division", because it divides what is already there in the nucleus.