What is a faucet?
A bitcoin faucet is a reward system, in the form of a website or app, that dispenses rewards in the form of a satoshi, which is a hundredth of a millionth BTC, for visitors to claim in exchange for completing a captcha or task as described by the website. There are also faucets that dispense alternative cryptocurrencies.
The first bitcoin faucet was called The Bitcoin Faucet and was developed by Gavin Andresen in 2010. It originally gave out 5 bitcoins per person. [Source wikipedia]