what is the value of 0/0

Division is the inverse of multiplication. If a * b = c, c / a = b. If 0 / 0 = a, then a * 0 = 0. Any number times zero is zero, so a could be any number, real or imaginary. Since there is no definite answer, it is considered undefined.

Similarly, a / 0 where a is any number is undefined. Let's say a = 2. If 2 / 0 = b, 0 * b = 2. Since any number times zero is zero, it is impossible for 0 * b to equal two, no matter what b is.