I don't fully understand block chain but I know the basics. It's very much like traditional cash except digital, the rewards for mining and supporting the network are similar to how banks get interest on funds they hold or fees charged. Except with crypto currency the individual who does the work gets the reward so to speak, so it very much is a decentralized digital bank.
Just like any financial system as long as it has perceived value the system supports itself and supports other markets. That's why many people trade when say the US Dollar drops, because it affects subsidiary markets that rely on the value of the US Dollar. Now, as far as finances go that's just the tip of the iceberg. With crypto you also get security, as it's much harder for folks to "cook the books" as everything is encrypted. Not to say that won't stop people, just like counterfeits are still a thing today.
As far as mining, there is money to be made because the market is still new, so in a sense, everyone is helping to digitally print the new currency, whether it be in established or new markets.
Imagine the history of finances from the 1900's till now. With crypto all those experiences can happen all over again only digitally, so lots of cool things ahead.
That's pretty much my understanding too, though as timeshifter mentioned, currency is just the first application.
I'm far from being an expert either but I have read a lot on the subject. Here's how I would summarise my understanding of it ...
I think the first thing to understand is that a blockchain is just a type of database. It differs from a conventional database in that the data cannot be altered randomly. Instead, when transactions occur (such as the transfer of ownership of funds), a new layer (or block) is added to the database that records those changes. None of the earlier data is modified. Instead, each new block is added to the 'end', creating a 'chain' of records that contain every single data transaction, right back to the very first 'genesis block'.
A copy of the blockchain is held by every full node on the network, which may consist of hundreds, thousands, or even millions of computers worldwide. Not to be confused with miners, nodes are generally 'users'. In the case of cryptocurrencies, nodes are usually anyone running a 'full node' wallet. Each node connects to multiple nodes, sharing and comparing data. It 'trusts no-one', cryptographically verifying every single block and it is even able to ignore/ban any other node that attempts to give false or inconsistent data.
The job of the miners is to 'find' a new block, which involves validating and verifying ownership of pending transactions by solving immensely complex cryptographic problems and running the data through hashing algorithms until eventually a solution is found that fits like a jigsaw piece on the end of the blockchain. Just like solving a jigsaw, while finding the right piece may take time, everyone else can very quickly verify and confirm that the block 'fits'. The miner's reward for their effort/electricity is the transaction fees and, for 'mineable' cryptocurrencies, they are also rewarded with new coins. This system of mining is known as Proof of Work (PoW). Another commonly used system is Proof of Stake (PoS), where instead the
nodes are rewarded with new coins for 'holding' or 'staking' funds, giving a kind of interest on their savings.
What's really interesting is how this technology emerged and why there are now so many cryptocurrencies when, less than a decade ago, there were none. There's an age-old problem, known as
The Byzantine General's Problem, that illustrates the difficulty of maintaining information/data integrity without trust in a decentralised/distributed network. Essentially, without a central authority, how can you ensure data validity without trusting any network node? For a long time it was considered an unsolvable problem, but the anonymously released Bitcoin whitepaper changed all that, providing a working theory and code examples of how the problem could be overcome.
Personally, I think this technology has huge implications. To say that it's bigger even than the internet itself, I think is a gross understatement. Currency really is just "the first application". The deeper I get into studying it the more I realise the immense possibilities for building applications that could impact/disrupt just about every type of business.