Langlui's Big Board and Options Plays

[MrBigz]

I wanna learn more about calls and puts

it seems the most you can lose is the amount you invest but the potential gains seem massive.

questions:

can u sell at any time?

how do the percentages work - i.e. how does a $500 call on a stock that gains 20% turn into $40,000 profit

if you are wrong, do u lose a percentage of your investment based on share price when u sell or do you lose the entire amount?

thanks langy