If you've seen remedies labelled 6C, 30C or 200C, you've met potencies. They reflect how many times a substance has been diluted and succussed (vigorously shaken) during preparation.
Homeopathy uses the minimum dose — the smallest stimulus needed to prompt the body's own response — which helps avoid the side effects of stronger interventions.
Choosing the right remedy and potency is individual work. That's what a careful consultation is for.