what is forking attack? and different between forking attack and selfish mining?

what is forking attack? and different between forking attack and selfish mining?

I am a student who studies block-chain for these days.

I have a question about forking attack and selfish mining in mining strategies

as you see picture below

I don't understand why miner should send some money to a victim to do forking attack...

what does this means to do forking attack?

is it possible to do forking attack except sending some money to a victim?

and as below picture about selfish mining

what is difference between forking attack and selfish mining if miners exclude

to do send some money to a victim in forking attack?

can anyone help me to understand what M->B and M->M'(double spending) means??

and why do need it to do forking attack??

https://ift.tt/2IxZUyC