Answer:
First off, chromosomes are thread like structures found in the nucleus of a cell containing genes, which determine a certain characteristic, and DNA which is the chemical that is the basic unit of inheritance.
All human cells ( excluding people who has cell abnormalities etc. ) contain 46 chromosomes. However there's this one pair of chromosomes called the sex chromosomes ( X and Y chromosome ) which defines whether the person is a make or female.
A male will have XY chromosomes, but a female will have XX chromosomes. That's how you differentiate.