What Causes Light Menstrual Bleeding?

Hi, two days before I usually get my period, I had heavy menstrual bleeding early in the morning and really bad cramps like how it usually is when I get my period. Then throughout the day the bleeding started to get really light with only a little bit of blood coming out and clots when I would wipe or pee until I wasn t bleeding that much anymore and only had moderate cramps. The blood is the usual red color, but I just found this really weird. What does this mean?