The Greeks represent the consensus of the marketplace as to how the option will react to changes in certain variables associated with the pricing of an option contract. There is no guarantee that these forecasts will be correct.
There are five characters or factors which affect the prices of the options. Having knowledge of these greeks is good as it will help you to decide when to buy an option and sell it at a better price.
These five factors are fitted into pricing model of Black-Scholes to calculate the price of an option strike. I am not going to explain the Black-Scholes model to you as it can be very complex to understand and does not need much attention, we just want to understand how will these factors are going to react according to your position. These factors are delta, theta, gamma, vega and rho. I am going to discuss all these factors in my next posts.