The simple answer: it’s literally just free coins just waiting for you.
The method behind the madness, though, is a decision regarding marketing strategy. As a way to spread awareness to the relevant audience of potential investors and eventual enthusiasts, coin teams will, from time-to-time, do airdrops.
WHAT DO YOU NEED TO GET STARTED TO RECIEVE AIRDROPS?
An Ethereum Wallet: not one that is on an exchange.
It has to be a personal address that is ERC20 compatible because most of the tokens that are airdropped are ERC20 tokens, which are or were originally Ethereum-based ICOs. I suggest using MyEtherWallet to get started immediately
The Ethereum Wallet Must be ACTIVE. By active, I mean that you have to show at least some human use of it.
Lots of airdrops have checks in place to make sure that you aren’t just randomly generating a bunch of addresses and signing them all up to unfairly obtain more coins. This means that if your wallet doesn’t show activity, it might not receive the airdrop. Sometimes, coins will be explicit in what they look for, including some type of balance in the account.
A Telegram Account : I’m sure there are amazing reasons why Telegram is the chatting tool of choice for many of these ICOs. The coins want to boost the audience count.
Usually, these airdrop coins will also require you to sign up for their Telegram accounts. Until you receive the coin in your Ethereum wallet, do not leave the Telegram accounts or you risk disqualification for the airdrop.
A Twitter Account : Similar to the reasons behind the Telegram account, many of the airdrop coins will also require you to follow them on Twitter. Some of them will even ask you to retweet some tweet.
An email address. sometimes airdrops will ask for your email, too. If you don’t feel comfortable with giving them your real email, just create a spam one. Remember the password, though; some of them actually ask you to confirm your email.
Obtaining and Withdrawing Tokens
Usually, it takes about 1–2 months after the end of the airdrop before you receive your tokens. This is primarily due to the fact that many airdrops occur before or during token sales, in conjunction to spread awareness. And tokens are not distributable until the end of a token sale anyway (I’ll write a separate piece on Token Sales, or ICOs).
To check your wallet info and see if the token has appeared in your wallet yet, just go to Etherscan. Type in your ETH address into the search box.