We're a soul that came into this world with two tickets.
One is called Life which is ticket to vacation and Second is called Death which is ticket to return home.
Let's see it in practicality of life, when a kid is told that they are going on a vacation you can see them happy & full of energy, also you may have notice they'll get frustrated and beg you to extend the vacation duration when they'll come that days are about to get over.
Now let us get straight to the point.
Using the first ticket, everyone is born on earth to enjoy their vacation & to do things they want to do this lifetime.
It's not easy to get born, you maybe very well aware of the biology of reproduction (millions of sperm, race, etc). In common case, one soul is lucky & in rare cases it's more than one that are born out of billions...