In a layman's term: it's all about Supply & Demand my friend.

The supply of Bitcoins is finite while more and more people want to hold a pie of it. So the demand is increasing in leaps & bounds, increasing the price of Bitcoin. If the demand will decrease then price will go down.

If you ask about intrinsic value, then there is no such value of Bitcoin. It's the trust of people which gives value to it and demand increases the value.