There is no real difference between the two as they both essentially use Cryptography. "Crypto" is just a shortened version of the word Cryptography. However, there has started to become a distinction between the two words, there are a lot of different tokens and blockchains and they have either been hacked or are run by scammers, very few are successful. These are often referred to as "crypto" whilst Bitcoin is seen as its own separate digital asset. We highly recommend holding Bitcoin rather than any other cryptocurrency as they potentially could be scams. Some casinos will allow you to use stablecoins such as USDT (Tether) which reflect the value of a US dollar which makes the bonuses easier to read than using a Bitcoin denomination.