In English, the simple present often implies a general truth, regardless of time. While the present continuous strongly implies that the statement is true for the present, and weakly implies that it was false in the past.

From your profile you apparently speak Danish, right? Note that, in Danish, this distinction is mostly handled through adverbs, so I’m not surprised that you can’t tell the difference. Easier shown with an example:

Danish	English
Jeg læser ofte.	I read often. (generally true statement)
Jeg læser lige nu.	I’m reading right now. (true in the present)