The most left coin is a Taol (the square golden one) and will be used with merchants from other countries to buy special resources. The silver coin (the middle silvery triangle) and copper coin (the last coppery one) are a normal currency and can be used in dialogues with some merchants to buy goods.
That's just an example, there are also other kinds of coins that are not shown in this video or the image because are "special" coins that you will find in game (like the waterdhavian halfmoon) that works only on specific npcs and collectors
There are also bankers that will accept any coin you bring, many have actual value for the game world mind you, and exchange in other type of coins. Also, the banker will have the funcionality of paying taxes and money you own to the city (like fees or other services,see Housing and persistent maps topic) throught it, so if you are unable to login for a long period of time and are afraid that your house permit will expire, have no fear. So long you have money in the bank account will be automatically paid for you
