Today our leader @sirknight created a cryptocurrency, although you may believe it, it is possible as any software application, either as a possible attempt to take control of the world with the next world reserve currency, or as a currency for a community niche specific or simply as a recreation or hobby.
Most digital currencies today use Bitcoin's pioneering blockchain technology. In simple terms, the chain of blocks is a shared public book of each transaction that has taken place throughout history.
This chain is stored by each complete node in the network so that the world people can know if a person who is trying to send coins, really is the legitimate owner of those coins.
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There are a lot of different options to customize your currency so that it is a unique digital currency and so that it can fit better in your purposes.
You can set the block reward and choose if you want the miners to use one of the various "proof of work" algorithms to protect your network, or that the miners win prizes as "participation proof".
You can choose the amount of data you should allow in each transaction, the size of the block, the maximum supply of coins, the difficulty and how it will change over time to control the rate of issuance of new currencies, the level of the rates and if they destroy or "recycle" for the miners, and so on.
Most of the services that allow you to create a cryptocurrency secured by an established Blockchain, will allow you to control some of these parameters within certain limits, but none of them will give you complete control and flexibility above all. On the other hand, there are some distinct advantages over the use of an established blockchain.