There is a limit to how many Bitcoin (BTC) exist today and how many can exist in the future.  The current amount of BTC in circulation today is around 16,451,000 as of July 15, 2017.

The max BTC that will ever be produced/mined is 21 million.  21 million may not sound like a lot when you consider it may one day replace Gold as the store of value globally but this has been solved by allowing each BTC to be broken down into parts of a coin.  Think of this as the same as having 1 x $100 dollar bill versus 100 x $1 dollar bill.  The current price of 1 full Bitcoin as of July 17, 2017 is around $2160 US.

With the current exchange rate I could send you a full Bitcoin worth $2160 or I could send you .1 BTC worth $216, or .001 BTC worth $2.16.  You can see by this example that you can send and receive any comparable denomination with the feature of fractional coins or parts of coin.

The main point you should take from this post is that there is a limit to how many BTC can be produced and this can help to solve the problem of governments printing money at will which causes the money in your bank account, your life savings and your retirement to have less purchasing power as new dollars are printed and pumped into the market.  This also reduces the impact of counterfeit currency as Bitcoin is nearly impossible to counterfeit.