Altcoins
Altcoin is shorthand for any cryptocurrency other than Bitcoin.
In depth
The term covers everything from Ethereum to obscure micro-cap tokens, so it says little about quality. Some altcoins introduce real innovations (smart contracts, privacy, speed); many are copies or experiments. They tend to be more volatile than Bitcoin in both directions.
Why it matters
Knowing that "altcoin" is a catch-all, not a category of merit, helps you evaluate projects individually.