As we see in the world the stock prices and the exchange rates and all of that is changing day by day. That means BTC prices also change, as they are a form of cryptocurrency it has to change just like any other currency has to. Therefore it is pretty common to see the changes.
But why does it change so often?
The prices change because it is volatile, this means that it will it is liable to rapid changes, and not just this, like we talked about many other things are subjected to being volatile. Even though the market for this is relatively small it is still volatile, and nowadays it is becoming more stable.
How is the price determined?
BTC price is not the same as its value, it is actually determined by the market. This means the demand and supply of a market. When the price is being determined there are other factors to take into consideration like how much buyers are willing to pay in the future and so on. Basically it is the on going interaction between buyers and sellers that determines a specific price.
How has it changed over time?
We know that nothing stays constant as time goes on, it is always bound to change. The value of it will change depending on its scarcity and the usefulness of it. If it is more useful and scare the demand value increases. So if we take into bitcoin price charts we can see that it is increasing overtime.