A put option gives its holder the right, but not the obligation, to sell a certain instrument (like a stock or a future), called the underlier or the base contract on or before a certain expiry date at a certain strike price.
If you hold a position in a Put, your potential loss is limited to the price you paid for the option, so called option premium, and in most cases your potential profit is limited as well, since the price of the underlier usually cannot go below zero. The profit you get at expiry is calculated as strike price - base price or zero if the base price is higher than the strike.
See also european vs american options, call option.
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The screenshot shows the following portfolio:
European put struck at 10.000 with expiry in 30 days
This is an excerpt from iOptioneer option trading reference application. In order to build the real-time dynamic strategy graph and run simulations you will need to download the application from App Store.