Arbitrage is the act of buying and selling something at the same time to make a profit. The idea is to buy something at a low price and sell it at a higher price. The difference is the profit.
Airbnb arbitrage is renting a property yearly and then turning it into short-term holiday rental. The goal is to have the revenue from short-term rentals exceed the cost of renting, furnishing and managing the property. Here's an example of how much you could earn with Betterplace Airbnb Arbitrage investment products.