Bitcoin exactly happens to be a token issued from the Bitcoin Blockchain, nothing more nothing less.

This token may be programmed to execute different functions, hold different values and uses implicitly not to forget its ability to be divisible into a million portions for trade.
 trade reason Bitcoin is so valuable today is that there can only be 21 Million Bitcoins within the network. After the last Bitcoin is purchased, people may begin trading in less which would make it more valuable. This value increase would be due to the limited supply of Bitcoin, matched with unlimited demand for this cryptocurrency