Hamming distance required for error detection and correction

I have already asked a pair of questions on the hamming distance, hamming code, valid and invalid codewords on this website, because I cannot understand those concepts fully, and in a few weeks or less, I am going to have an exam also on those topics, I really do not understand. I have tried to take a look to wikipedia articles, but it is, for me, quite complicated to understand.

My question this time is more concrete. I have a figure, representing how many errors can we detect and correct according to the hamming distance. The thing I am not understanding is why, for example, with an hamming distance of 3, we can just detect 2 bit flips and correct 1 bit flip. I know there are 2 formulas (that you can see in the picture), which bring us to that result, but I would like understand why those formulas are correct. Why, with an hamming distance of 3, we can just detect 2 errors and correct 1.

This is picture: