Combinations are trades constructed with both a call and a put. There is a special type of combination known as a “synthetic.” The point of a synthetic is to create an options position that behaves like an underlying asset, but without actually controlling the asset. Why not just buy the stock? Maybe some legal or regulatory reason restricts you from owning it. But you may be allowed to create a synthetic position using options.
When purchasing put options, you are expecting the price of the underlying security to go down over time (so, you're bearish on the stock). For example, if you are purchasing a put option on the S&P 500 index with a current value of $2,100 per share, you are being bearish about the stock market and are assuming the S&P 500 will decline in value over a given period of time (maybe to sit at $1,700). In this case, because you purchased the put option when the index was at $2,100 per share (assuming the strike price was at or in the money), you would be able to sell the option at that same price (not the new, lower price). This would equal a nice "cha-ching" for you as an investor.
* Sell orders are subject to an activity assessment fee (from $0.01 to $0.03 per $1,000 of principal). Trades are limited to online domestic equities and options and must be used within two years. Options trades are limited to 20 contracts per trade. Offer valid for new and existing Fidelity customers opening or adding net new assets to an eligible Fidelity IRA or brokerage account. Deposits of $50,000-$99,999 will receive 300 free trades, and deposits of $100,000 or more will receive 500 free trades. Account balance of $50,000 of net new assets must be maintained for at least nine months; otherwise, normal commission schedule rates may be retroactively applied to any free trade executions. See for further details and full offer terms. Fidelity reserves the right to modify these terms and conditions or terminate this offer at any time. Other terms and conditions, or eligibility criteria may apply.
However, options are not the same thing as stocks because they do not represent ownership in a company. And, although futures use contracts just like options do, options are considered lower risk due to the fact that you can withdraw (or walk away from) an options contract at any point. The price of the option (its premium) is thus a percentage of the underlying asset or security.