@StarJo – That's because it uses infrared light, and we can't see this kind. It just travels through the air unseen.
If someone walks between the remote and the TV, then the light gets interrupted and you can't change the channel until the person has moved. Also, if any furniture is in the way, you'll have to move it, because infrared light can't travel through it.
However, I do remember a cool trick I learned in physics. If you stand in the room with a mirror in your hand and adjust it so that you can see the screen in it and then aim the remote at the mirror image, the remote will work. This is because the light bounces off the surface and gets redirected toward the screen.