Bitcoin is a unique cryptocurrency in that only a finite number of them will ever be created. It is also decentralized, meaning that it is not subject to the control of any particular entity. There are many other cryptocurrencies out there, but none have achieved the same level of success as Bitcoin. It was the first cryptocurrency and has a considerable market share. As bitcoins get saturated, the demand for other cryptocurrencies will increase. The growth rate of other cryptocurrencies will be slower than bitcoin, but it does not mean that you will not profit from it. It all depends on the market trend and how much spotlight the particular cryptocurrency gets.