What is Arbitrage Trading?

Is a strategy of foreign currency trading that use the barrel of a draw, where the trade in doing in a minimum of two different currencies with the opposite position. If taken a very simple example is like the Premium Arbitrage and Pertamax the same time, while premium price rises and price rises pertamax not, then most likely that in the not too long so what happens is, if not prices go up pertamax which means premium prices back down, that under such conditions that must be done by an arbitrage trader is n Buy Sell Premium Pertamax. Perhaps it is an example that may be less appropriate to describe the basic principles of this teory.