How Do People Get Freckles...?

Well I don't go in the shower often, but now when I look at my arms they already have freckles (not everywhere, scattered) but now i see some freckle looking dots on my arms... they are brown little dots and is it possible i got them from not showering or going out in the sun? i never go out in the sun and i stay home... do i have a disease? how do people get freckles?
i did stay in the car where it was really really hot with 1 window open sweating for about 40 minutes today... but i was not directly in the sun!