Bitcoin trading occurs on exchanges. These exchanges accept your fiat currencies (like USD and EUR) in exchange for a cryptocurrency (like BTC). These exchanges maintain a liquid pool of bitcoin, allowing users to withdraw their bitcoin at any time. Investors who wish to trade on that exchange can deposit bitcoin into their personal wallet on the exchange, or make a wire transfer to the exchange’s bank account. The exchange notices this transfer, then credits your account.
The term altcoin has various similar definitions. Stephanie Yang of The Wall Street Journal defined altcoins as "alternative digital currencies," while Paul Vigna, also of The Wall Street Journal, described altcoins as alternative versions of bitcoin. Aaron Hankins of the MarketWatch refers to any cryptocurrencies other than bitcoin as altcoins.
In this guide we don't want to deal with social loss risk, so use the FCA-regulated, London-based bitcoin derivatives exchange CryptoFacilities. They offer contracts with 2% margin requirement (50x leverage) as well as a 15% margin requirement (6.5x leverage). They are 100% bitcoin based, but they don't accept US customers. Sign up here to get started: