A straddle holds a call and a put at the same strike and expiration. Bought, it profits when the stock moves further in either direction than the combined premium paid; its price is the market's clearest quote of the expected move.
The at-the-money straddle's price divided by the stock price reads out the implied move for that expiration, which is why event analysis leans on it. As a position, the long straddle pays double time decay for its double-sided exposure, so its disciplined use concentrates where a known catalyst sits inside a few sessions; research places the pre-earnings straddle edge in the final three to five trading days before the print.