Cryptocurrency faucets or bitcoin faucets and altcoin faucets are all just ways to encourage others who may never of heard of bitcoins or altcoins to try them out. The concept is easy, a site has a set amount of cryptocurrency to give away for free. Now the user will either need to stay on the page for a bit, or complete a captcha and wait as well for a very small fraction of a coin. Normally if it's Bitcoin, you'd get 0.000001 or a few cents worth of bitcoin and if it's an altcoin, you might get a whole coin or more.
Just becareful, some sites are just using you to fund their Google Adsense wallet, and tricking you into helping them, by clicking ads or otherwise conning you into carrying out a engagement activity on their site that inturn helps them make more money, while giving you a fraction of a cent. Not to mention, there are also other sites who will try to load malware by saying they have the wallet for the altcoin you're recieving for free, that turns out to be anything but. Always download wallets for cryptocurrency from trusted sources, most sites will not warn you if they want to take advantage of you.