Just on a basic level, have you tried pressing them or sliding them?
What exact model of Samsung do you have? Features change from model to model and this may be a feature of your device. I have a Samsung and I have never seen circles at the bottom of my screen semi or otherwise. Plus by telling us what device you have we may have a forum here specific to that device, which would allow you to ask this question to others with the same device.
Are the always there, just when you're on your home screen, right after you close an app? When are you seeing them?