A cryptocurrency is a digital currency that is secured by cryptography, which makes it nearly impossible to counterfeit or double-spend. Most use blockchain technology, a digital ledger enforced on a vast network of computers controlled by the people using what they call a node. Cryptocurrency aren't just currencies but more of a digital assets.
Cryptocurrency is a term coined for digital assets. Not all crypto is currency. Think of land in Manhattan NY, on that property there is a building, in that building there are companies, and those companies earn US dollars. Now think crypto; the US dollar is digital currency, the land is digital property, the building is a digital platform, and the companies are digital applications. There is different types of crypto that do different things. Bitcoin is like property in cyber space, and a stored value that appreciates over time, based off a proof-of-work protocol. Ethereum (ETH) is the digital platform that anyone can build on. Coins like Polkadot (DOT), Chainlink (LINK), Polygon (MATIC), VeChain (VET), etc. are the applications. Crypto that is strictly digital currency are coins like Litecoin (LTC), Ripple (XRP), Dogecoin (DOGE), etc., some having different types of protocols. All those coins mentioned are all digital assets with different values that can be traded for other digital coins or fiat currencies like the US dollar, Euro, British pound, etc..