[curiousgal]

A put is a option contract that gives its holder the right to sell a share at a certain price (strike) within a certain time (maturity for American options, European options can only be exercised at maturity). If you buy a put of strike 100 and a stock is at 90 you can exercise it thus selling the stock at 100 which is higher than its actual price.

So when you buy a put you are betting that the stock is going to go down. Each put usually gives you right to sell 100 shares, and since you can buy/sell the contract itself, you can easily get leverage when compared to actually trading the shares.

Without knowing what the strike prices and how much he paid for those contracts you can't really determine how much he is going to gain/lose. His gain is capped though as TSLA cannot go below 0.