Basics
History
Before starting, I believe it's important to understand the historical context that motivated the idea of blockchains and eventually gave birth to Bitcoin (the first cryptocurrency). The following three articles, when read in order, do a great job at painting the initial picture that will inform everything else:
Blockchain
An important concept to have a basic understanding of is a blockchain. Here are a few good breakdowns of what a blockchain is, how it works, etc. Don't worry if this doesn't completely make sense — you should be good for now if you just grasp it at a high level.
After reading some of these pieces you might be wondering why anyone would care about decentralization so much. Here's an article on why it's important: Why Decentralization Matters
Wallets & Keys
Just like you have an email account with Google, you can have an "account" in the blockchain, which is referred to as a wallet. They are called wallets because they store your (digital) money. Like your email account, your wallet consists of a public address (email address) that everyone knows, and a private key (password) that only you know. In the blockchain, an address is usually a long string of random letters and numbers. It usually looks like this:
17qtBGaDvsebQvx9bnBMNMsfzWqmDZuEWaOn the other hand, your private key is 12 random words, as it is very secure and still easy to store. A private key (or sometimes called 'seed phrase') looks like this:
igloo collapse practice feed shame close despair creek road again ice leastPrivate keys are extremely sensitive information because anyone who has access to it can steal all your funds, in the same way a hacker with your email and password might be able able to steal your information. This is why people usually write the private key on a piece of paper and then store it safely, instead of keeping it in their computers or phones digitally where it could be potentially hacked.
Here are some good articles with more details about how wallets & keys work.