Take an example of a stock trading at $100.
A: You can buy this stock normally, and if it goes to $150, your gain is 50% on your investment
B: You can buy deep ITM leap call, say, 12 months out call with strike price of $50. In this case, your cost is likely going to be $55-$60. The premiums is therefore only $5-$10.
Now, if stock also moves to $150 within 12 month, your leap will be worth at least $100. So, your gain is 80-90%, essentilly twice as much as what you would gain if you were to just buy normal stock