I'm confused about the main difference between using def__mul__() and def__rmul__() when adding them to a class

class NumString:
    def __init__(self, value):
        self.value = str(value)

    def __str__(self):
         return self.value

    def __int__(self):
        return int(self.value)

    def __float__(self):
        return float(self.value)

    def __add__(self, other):
        if '.' in self.value:
            return float(self) + other
        return int(self) + other

    def __radd__(self, other):
        return self + other

    def __iadd__(self, other):
        self.value = self + other
        return self.value

    def __mul__(self,other):
        self.value = self * other
        return self.value

    def __rmul__(self,other):
        self.value = self * other
        return self.value