The Strike Price is the price at which a derivative contract (Example: an option contract) can be exercised.
For the options market, a call strike price is the price at which the underlying security can be bought (at or before the expiration date).
Regardless of the underlying security price, you can exercise your option and buy the underlying security at any moment (for an American option) at the strike price.
A put strike price is the price at which the underlying security can be sold (at or before the expiration date).
The strike price is one of the most important variables that influence the option price or premium. The other variables include Time until expiration date, volatility of the underlying asset, dividends and interest rates.
