Arbitrage is a financial and economic concept that refers to the practice of exploiting price differences for the same asset, security, or commodity in different markets to make a profit with little or no risk. In essence, it involves taking advantage of discrepancies in market prices.

Here's how it works:

1. Identifying Discrepancies: Arbitrageurs constantly monitor various markets or assets to identify situations where the same asset is priced differently in different markets or at different times.

2. Simultaneous Transactions: Once a price discrepancy is identified, the arbitrageur buys the asset at the lower price in one market and simultaneously sells it at the higher price in another market.

3. Riskless Profit: Because the arbitrageur is buying and selling the same asset at different prices simultaneously, they lock in a riskless profit, as they are guaranteed to make money regardless of future price movements.

4. Quick Execution: Arbitrage opportunities often exist for only a short period, sometimes just seconds or minutes, so quick and efficient execution is crucial.

Arbitrage can occur in various financial markets, including stocks, bonds, currencies, commodities, and derivatives. It's driven by the principle of the efficient market hypothesis, which suggests that in a perfectly efficient market, there should be no arbitrage opportunities as prices should reflect all available information accurately.

Common types of arbitrage include:

1. Spatial Arbitrage: Exploiting price differences in the same asset between different geographic locations. For example, buying a product in one country where it's cheaper and selling it in another where it's more expensive.

2. Temporal Arbitrage: Capitalizing on price differences for the same asset at different points in time. This might involve buying a stock at the closing price and selling it at a higher opening price the next day.

3. Statistical Arbitrage: Using statistical models to identify discrepancies in asset prices and make trades accordingly. This often involves pairs trading, where two correlated assets are bought and sold based on their historical price relationship.

4. Risk Arbitrage: Also known as merger arbitrage, it involves capitalizing on price differences between a company's stock price before and after a merger or acquisition announcement.

Arbitrageurs play a crucial role in financial markets by helping to ensure that prices across different markets remain closely aligned. Their actions tend to reduce price discrepancies, making markets more efficient. However, arbitrage opportunities are becoming scarcer due to advances in technology and increased market efficiency.