Steemit is a great platform that in many ways has its own citizenry. But an important aspect of being a citizen is being well educated in how the system you are a part of works. Because of the nature of the platform, many will be getting on Steemit with absolutely no idea about cryptocurrencies. To that end I'm starting this series to make short lessons that might be of value to those getting started.
Blockchain is described in wikipedia as the following: a distributed database that maintains a continuously-growing list of records called blocks secured from tampering and revision. Each block contains a timestamp and a link to a previous block.
We're going to break this definition down and then use a basic analogy to make sense out of exactly what is being done here and why it is so revolutionary.
The first part of the definition reads "a distributed database...". What is meant by this?
Distributed Databases
A database is simply organized information. Think of it as a room full of digital file cabinets that can sort anything from pictures to numbers. Databases keep information neat by having it categorized, often in different ways, such that the user can find pertinent information on any given item in the database with relative ease. It's much the same way files in a file cabinet are usually in some sort of order, often alphabetically or by date.
A distributed database is a database that is not in one location. Now, it's true that most databases will have some sort of backup, especially if they're important. But what we mean by a distributed database is a little different. We mean that a copy of the database that is more or less the same (with, perhaps, minor differences) is shared by a large group of people.
By shared, we mean that each person has a complete copy of the entire database, making the database extremely protected. Think about it. If something happens to one or even several user's computers, the database itself is still safe so long as even one computer is still running the database.
Blocks
The other word in the definition that might catch some people off guard is the word blocks. If the database is the room of file cabinets, then each cabinet itself would be a block. A block is nothing more than a chunk of information in the distributed database. Each block is connected to the one before it via a link, making a chain (what we call the blockchain).
Great... But What Does it Have to Do With Cryptocurrency
The blockchain is basically where the value of cryptocurrency is stored. Every cryptocurrency coin transaction that occurs is "coalesced" into a block, which is then added to the previous block via a link. The miner who does this is part of the distributed database that I was talking about, and generally receives a reward in the form of new cryptocurrency for her efforts.
Don't worry if the previous paragraph didn't make complete sense to you. We'll get more into it in future lessons.
More Reading
Consider reading 
Other Posts in This Series
Cryptocurrency for Absolute Beginners: ....So What Is Cryptocurrency, Anyway? (Part 1)
Cryptocurrency for Absolute Beginners: ....So What Is Cryptocurrency, Anyway? (Part 2)