An airdrop is a method for distributing cryptocurrencies to users for free. This can happen in several ways. In some cases an airdrop is made simply because a user holds a certain kind or cryptocurrency, and in some cases airdrops are done for owners of specific wallets. Some airdrops are the result of a hard fork to a blockchain, with owners of the current coin receiving an equal measure of the newly created coin after the hard fork occurs. The best example of this was the creation of Bitcoin Cash. There are also public airdrops, where users typically have to perform some action, such as liking or sharing a coin’s website on social media. Airdrops are very common in ERC-20 coins. Some people have called airdrops a PR stunt, but in many cases they are considered a suitable method for distributing new coins.