An airdrop is a way to distribute coins. End users can generally get coins for free or in exchange for a small task, such as subscribing to a newsletter, sending a tweet or inviting other people via a personal affiliate link.
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A block explorer is an online service to track blockchain transactions. It usually is a website where you can see all the new blocks that are being created. You can also search for transactions and wallet addresses. The best-known block explorers are blockchain.info for Bitcoin and etherscan.io for Ethereum.
With digital currency, there is a risk that the holder could make a copy of the digital token and send it to a merchant or another party while retaining the original.
An altcoin is any cryptocurrency or token created after the Bitcoin was developed.
Launched in 2015, Ethereum is the world's programmable blockchain. Like other blockchains, Ethereum has a native cryptocurrency called Ether (ETH). ETH is digital money. People all over the world use ETH to make payments, as a store of value, or as collateral. But unlike other blockchains, Ethereum can do much more.
Cold storage refers to storing cryptocurrency on a place where the private key cannot be accessed via the internet. This can be done on a hardware wallet, paper wallet or software wallet in an offline environment.