Why do people even use currency?
Because it's so much easier than barter! Look I'm a chemist by trade. If I have to trade hours of chemistry labor for a certain amount of vegan meatballs it's going to be pretty challenging. I need to find a vegan meatball sales man willing to accept hours of chemistry labor to make the trade happen... Instead we all collectively decide it's better to have currencies we can all use and then trade for the currency as a medium of exchange. This makes life a lot easier!
Who gets to create currencies?
For 100 years or so the only people creating currencies that are adopted on a wide scale are governments (or the private banks they employ). They print money. They get to print the money because they are in charge. You're born under their rule and they print it as they see fit. Sometimes they do good things with it and you experience a nice life. Sometimes they enact horrible plans and you're stuck rioting as your national economy goes through a hyperinflated death spiral. Either way you're not really choosing your currency when you're born. You simply have the local currency and that's your option.
But an interesting thing happened with bitcoin, then it's clones, and then it's alts. Government currencies suddenly had a new competitor. They used to have some of that competition back in the Wild Cat Banking era, when private banks issued currencies all the time. This was actually a pretty good time for people. There were booms and busts in those currencies, but it was generally prosperous because people could invest as they saw fit in good private currencies and some fortunes were made. But the USG consolidated that back in the early 1900s. So, private currencies isn't a new thing. It's just that now there's new technology that allows it and makes it fairly simple to implement globally.
Blockchains and Crytpo Currencies
What's a blockchain? What's crypto? A blockchain is a big ledger. A ledger is basically a data table that keeps track of individual accounts, what's been issued, and who owns what. The blockchain starts pretty simply and over time it adds transactions and new people. The whole block chain is made up of individual blocks. Each block keeps information that was stored in it during that time period. Sally sent Jim 15 tokens. Jim sent Jane 10 Tokens. The platform generated 1 new token would be some of the transactions stored in an individual block. Every X minutes a blockchain will store what happened on the chain in that time period in a new block and add that block to the chain. Each block chain determines how much time is stored in each block.
It would be like saving just the changes to an excel table rather than the whole table every 5 minutes, and storing all those series of changes in lots of little linked files.
The crypto part comes from the fact that people could try to corrupt these data tables to show something like everyone transfers aggroed 10% of their money.' If you're aggroed that's awesome, but if you're everyone that's bad. So, to make that a challenging or practically an impossible task blockchain technologies also incorporate cryptographic techniques through "hashing" that make it extremely difficult bordering on impossible to crack the "crypto safe."
Let's talk about stocks for a second
Another investment type is a stock. Why would you invest in a stock? The simple answer is that you believe the stock can make more money than you can with the money that you have. You inherently believe that a group of a people working on solving a problem or set of problems by offering a product or service to the market can do a better job earning money than you. This is likely true.
You alone aren't a team of people backed by capital working on a project so it's more likely that a company could take your money and invest it into their projects and earn you more money back than you could just by yourself. There are obvious exceptions to this, but if you're not the business type, but happen to have some extra cash companies can put your money to work and so you're happy to buy shares in them. One of the main things determining the value of one stock compared to others is how much money can you expect to earn from owning one share of the company either through price increases or dividends.
Ultimately though you like stocks because they are a store of value, you think they will make more money than simply hoarding cash, and you think that the stock will likely go up in value as people work in the company.
Cryptos are a combination of a stock and a currency
Most of the time you don't trade 15 shares of IBM for your kitchen remodel. There's not really anything stopping you from doing that, but it's really not convenient. That's because stocks aren't much of a currency. Yes they have value, yes they are transferable, but there's really no way to quickly or easily get them from one person to another.
A crypto currency has a neat role of being both a stock and a currency. It's a stock because essentially you own a portion of the blockchain in proportion to the number of shares you have vs everyone else. If you own 10% of the crypto tokens on a block you essentially own 10% of the blockchain. Unlike stocks though if I want to transfer that ownership to you I can do it quite easily. I click a button or type in a command and suddenly 
Cryptos vs Government Currencies and deflation vs inflation
Before 1971 every government dollar was backed by a store of gold. You could walk into any bank and say "Hey, um, I don't like this dollar bill, and I'd like to exchange it for gold." They'd give you gold. You do that now and they give you funny looks. That's because the USG took the USD off the gold standard in the 1970s. Without the gold standard to keep printing in check the government decided to print and print and print money. The USG/FED now prints 160M USD a day. It's a lot of money, and it leads to a lot of inflation. Essentially the money in your wallet will be purchase fewer goods and service tomorrow than it will today!
Crypto currencies have a range of answers to this, but generally speaking they have a cap on the number of tokens that can be printed and the currency generation is slow. This makes crypto currencies deflationary relative to government fiat dollars. That means that the amount of money in your crypto wallet today will buy more goods and services tomorrow than it will today. This helps give crypto currencies value because if you have the choice of holding your money in a spot guaranteed to lose value or likely to increase in value it's an easy decision.
Other differences between Government Dollars (fiat) and Cryptos)
There are some key differences between these systems too.
Government Fiat Dollars are generally tracked and your ID logged everywhere. Crypto is psuedoanymous. If I want to buy weed with a credit card it will register everywhere. I might get arrested. If I buy weed with crypto then people might see that
This is important if your government makes any retroactive laws. What you did that was legal at one point now gets you arrested. You made a political donation to the opposition! Poof! Jail for you... It would have been safer if it was anonymous or psuedo anonymous.