If the same thing has a different price in two different places, you can profit by buying it at the cheaper place and selling it at the more expensive place.
Arbitrage is the practice of taking advantage of a price difference between two or more markets.

For example, if you find that stocks from some company are traded at a lower price in one market than in others, then you can buy those stocks at that market and sell them in the other markets at a higher price, thus making a profit from the price difference. That’s what arbitrage is.

An exchange arbitrage is a commonly known trading strategy based on the differences between the price for the same asset at different exchanges (the price difference is called "spread").

Arbitration remains a very interesting area of finance.
By limiting risks to a minimum, the operator can generate substantial profits by multiplying small capital gains.
However, it remains much less mediatized than traditional trading. Moreover, arbitrage helps to correct market imperfections and helps markets to achieve perfect efficiency while improving their liquidity.

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