The body is made up of millions of cells.
Each body cell has copy of 46 chromosomes.
The 46 chromosomes are actually 2 complete sets of 22 non-sex chromosomes and 1 sex chromosome (commonly called the X or the Y chromosome)
Each ‘set’ of chromosomes has been inherited – one set from Mum’s egg; one set from Dad’s sperm. Imagine that this is like having 2 suits of cards – one red; one black. You would have one red King; one black King; one red Queen; one black Queen. Imagine that the sex chromosomes are like the 2 jokers stuck on the end.
Sex cells (eggs and sperm) only have one set of chromosomes – this is so that when an egg and sperm come together; they merge; providing one ‘set‘ each; and the new cell that results (and ultimately grows into the foetus) has the correct number - 2 sets.