there are two possibilitis, but without knowing the full context of what/where/how you heard it. not many can guess.. but here are some suggestions


binary options are the scam of the trading market.
there has been an increase of advertising these scammy 'binary options' trading platforms in the bitcoin industry

or

it is just a way of saying "digital" mining. as oppose to mineral mining.
as a way of easily expressing the difference without having to use cryptic words like blockchain/crypto