A Bitcoin Faucet is a website that gives you Bitcoin or other cryptocurrencies for free. To receive a small amount of Bitcoin, the faucet requires that you type a CAPTCHA code every time you use them. You just have to enter the characters shown in the CAPTCHA and then click on the claim button to receive a small amount of free Bitcoin. Faucets put ads on their websites so they can pay you.
Bitcoin rewards are given in form of satoshis which is the smallest unit of Bitcoin (0.00000001 BTC). The amount of Bitcoin faucet give varies from about 10 satoshis to more depending on the website and the amount could fluctuate according to the value of Bitcoin. You have to provide your Bitcoin wallet address and the free Bitcoin amount will be credited to your wallet once the minimum amount of payment is reached. Bitcoin can be also directly credited to a Bitcoin microwallet as Coinpot, then you can withdraw to your Bitcoin wallet address once the minimum amount of withdrawal is reached. Bitcoin microwallet is helpful because it saves some transaction fees.
Bitcoin rewards are dispensed at various intervals of time, from few minutes to few hours. There are faucets that give alternative cryptocurrencies as Litecoin or Doge.