A blockchain is a distributed database. You can think of blockchain as a decentralized digital ledger that records all data that go through its network. Data is stored in the form of blocks, that then get chained together, hence “blockchain”.
An incorrect comparison. Bitcoin is a cryptocurrency that is based on blockchain technology. Most cryptocurrencies are based on blockchain networks, but this technology may be used in a variety of other sectors.
Blockchain based cryptocurrencies, which facilitate blockchain gambling are as legal as any other currencies, even if they are unregulated in most countries. Decentralized gambling sites are also legal, albeit unregulated too.
It might not be the definitive answer to everything, but it may offer efficient solutions to a multitude of industries. It is a relatively new technology, so there are still a lot of developments and technological advances due.