A diploid cell is a cell that contains two sets of chromosomes. One set of chromosomes is donated from each parent. The diploid number is commonly abbreviated as 2n. For humans this equation would be 2n=46. Humans have 2 sets of 23 chromosomes leading to a total of 46 chromosomes.
Haploid cell is a cell that has only a single set of chromosomes. The cell contains only one member of each homologous pair of chromosomes (haploid number = n). For example - A human germ cell (a sperm or an egg cell) is haploid, which means it contains only one of each of the 23 chromosomes of the human genome, or it only has half the diploid (2n) number of a human somatic cell (which is 46).