This article published by Coinbase, What is Cryptocurrency?, is one of the best explanations of cryptocurrency and what is going on with decentralized finance.
Per this list of cryptocurrencies provided by Coinmarketcap there are 6,115 different cryptocurrencies at this moment. (I kept pressing the "Load More" button until it did not show that button any longer.) Of that total, 2,598 had some sort of market cap and a circulating supply.
Here is a video that explains wallets. Here is another video that explains wallets.