The name of this site refers to any crypto currency other than Bitccoin. They are collectively known as alt coins, alt as in alternative.
Each one has it’s own blockchain, use case and community. If you are thinking of adding any cryptocurrency to your portfolio it is important to research them fully. Check their price history and daily trading volume if they have already been listed on exchanges. A couple of sites you can do this one are coinmarketcap.com and coincap.io.
Are they still in the idea phase? Do they have a working prototype? Is there product already in use globally? Can their claims be verified externally to their website or social media accounts? 2017 saw a lot of growth in this space and 2018 will see this continue but as this article shows it can still be the wild west and you never know if you will ever see a return on your hard earned capital. Do your due diligence and only risk what you can afford to lose and if the coin you put your hard earned into delivers you could see a multiple X return.
Continue your education and may it lead to a wealthier and healthier future for you.