Bitcoin come from a technology that is known as blockchain. It is an online algorithm where mining happens. You can assume it as a mathematical problems with gradual increase in difficulty. Once you got an answer right, we call it blocks. Once a block is discovered, the algorithm moves to higher difficulty and it required even better power to solve the problem. The process is known as mining. Instead of human brain, the computing power is used for mining and to discover the blocks.

Now the difficulty of that algorithm is so high, it can't be solved by a normal computing power. You will need expensive rigs and a lot of mining power which make mining exclusive to a certain community. While only a minor percentage of people is mining, a whole lot more people is looking to earn in bitcoins which creates a robust demand where the supply is low compared to the demand. So people are willing to pay higher price for bitcoin which increases its price. So that is an overview of bitcoin as per my understanding and I hope it will help you understand the basics.