What is Conversion arbitrage, reversal arbitrage?

Conversion arbitrage buys the stock, buys a put and sells a call with the same strike and expiry, locking in the strike at expiry, when the call is rich relative to the put and the stock. Reversal arbitrage does the opposite: shorts the stock, sells the put and buys the call, when the call is cheap; it pays the stock’s borrow and any dividends.