What is an Airdrop?
Airdrops are usually coins/tokens that are distributed to the community for free or for doing some small tasks such as interacting in discord group/telegram/facebook/referrals etc..They are usually very profitable to just claim and hold the coins until they gain value
Castle Coin Airdrop
Basically,Castle Coin is distributing some of their coins for doing some small tasks such as Joining their group,interacting in social media etc..
You can earn up to 500 CSTL with the Airdrop. Currently the price of CSTL is 1000-2000 Satoshi : https://stocks.exchange/trade/CSTL/BTC
But note that this price will probably rise after the airdrop.
You can participate in the airdrop via this link (referral link): https://wn.nr/j26bz6 or via this link(non-ref):https://gleam.io/mlWL1/earn-cstl-coins-castle
Airdroptator.com
Talking about Airdrops,they are tons of them that pop's up everyday,but Airdroptator.com has made participation in these airdrops easier.
You can see more details about this awesome website in my other post: https://steemit.com/bitcoin/@pandatrex/introducing-airdroptator-com-the-best-airdrops-rotator-ever