Let's see the difference between sex and somatic cells :
All organisms that reproduce sexually form sex cells called gametes.
All cells in an organism other than sex cells are called somatic cells .
All organisms belonging to the same species have the same number of chromosomes in their somatic cells. When sex cells are formed, that number is halved.
That is why we can say that the difference between somatic and sexual cells of the same organism is given by the number of chromosomes they have: sexual cells have half the number of chromosomes than somatic cells.
Example:
In humans, all somatic cells have 46 chromosomes grouped in 23 pairs. They are said to be diploid.
Human sex cells (egg and sperm) have 23 chromosomes each. They are said to be haploid.