Cryptocurrency faucets are 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.
These faucets have you do menial tasks such as solving captchas, playing games, clicking on ads, or watching videos. For each task you do, you earn a small amount of Bitcoin, Litecoin, Dogecoin, Etherium, Monero, Dashcoin, Bitcoin Cash. ETC
Faucets can help introduce new people to bitcoin or to altcoins. A majority of faucets provide information to new users as well as offering them some free coins so that they can "try before they buy", experimenting with a test transaction or two before putting real money on the line. Since this whole experience is so new and a bit complicated to people, this is a beneficial way to promote digital currency and bring in new users.
Faucets are high traffic websites. It is not all that difficult to get a huge number of page views per day to a site which is giving away free money. If a website has other content or services to promote to Bitcoin users, especially new users, a faucet is a great way to bring them to make them familiar with a brand name.
Making a healthy profit from a faucet site on its own is a lot harder than just making a popular faucet, but it is still possible. There are a lot of these sites around today, so it's a very competitive market, and earning enough from advertising to cover the cost of the coins you are giving away and hosting costs is nearly impossible. Adding additional content to a website, or creating some kind of unique or interesting twist, is the only way to generate an income for a Bitcoin faucet.
Bitcoins are created as a reward for payment processing work in which users offer their computing power to verify and record payments into the public ledger. Called mining, individuals or companies engage in this activity in exchange for transaction fees and newly created bitcoins. Besides mining, bitcoins can be obtained in exchange for fiat money, products, and services. Users can send and receive bitcoins electronically for an optional transaction fee using wallet software on a personal computer, mobile device, or a web application.
Bitcoin as a form of payment for products and services has seen growth,and merchants have an incentive to accept the digital currency because fees are lower than the 2-3% typically imposed by credit card processors. The European Banking Authority has warned that bitcoin lacks consumer protections. Unlike credit cards, any fees are paid by the purchaser not the vendor. Bitcoins can be stolen and chargebacks are impossible. Commercial use of bitcoin is currently small compared to its use by speculators, which has fueled price volatility.
Bitcoin has been a subject of scrutiny amid concerns that it can be used for illegal activities. In October 2013 the US FBI shut down the Silk Road online black market and seized 144,000 bitcoins worth US$28.5 million at the time. The US is considered bitcoin-friendly compared to other governments. In China, buying bitcoins with yuan is subject to restrictions, and bitcoin exchanges are not allowed to hold bank accounts.
If you want to know more then check out the full Bitcoin Wikipedia article