I've discovered Bitcoin few days ago, but I am skeptical about few things, why would I invest money in Bitcoins at the end of the day, why would I converted money into Bitcoins?

If I want to bye stocks or invest money I can easily invest with real $. Why would I convert my $ to bitcoins?

If I want to gamble, I can simply gamble on websites that require $ as currency, why would I converted it to bitcoins?

What's the difference between Bitcoins and dolars? What does bitcoin bring to the table that real $ don't, less taxes, more income?