Altcoin, derives from the (alternative coin) word sequence. All crypto coins except bitcoin are called altcoin. Each altcoin has its own characteristics and values. What determines this value is how much the projects are developed and how much hope they are looking forward to.
When investing in altcoins, you need to do a detailed research. Because there are hundreds of frauds in the market, which are called non-promising and there are no promising altcoins. Taking these altcoins can harm you. You can think of it as buying a company's stock.
You can find altcoins on the market for many crypto money exchanges that exceed the demand limit and the market volume is high enough.