Somatic cells are the cells that make up all the structures, tissues, and systems of an organism. They each contain the full number of chromosomes and full amount of DNA for that particular organism, which may vary by species. As these cells divide, each new cell always contains the full number of chromosomes, thus making it genetically identical to other somatic cells.
Gametes are better known as sex cells, or eggs and sperm. These cells have undergone a very specific process that divides a whole cell into two cells, each containing one half of the chromosomes the other cells in the organism possess. This is important because when egg and sperm meet, they meld their half load of genetic material together to make one cell containing full genetic information. This cell merger is what humans call conception. The blended cell now divides and forms into a fetus, with genetic characteristics of each parent in its DNA.
As for exact chromosome numbers (I assume you are referring to humans).... A somatic cell contains a complement of 46 chromosomes. Gametes contain 23 chromosomes each. The sex of the baby being conceived depends on the combination of the sex chromosomes contributed by each parent. Females are XX, males are XY.