The takeout double is arguably the most useful and powerful tool you have to use during the auction.
This course will add significant detail to the material from Competitive Bidding, and introduce more ways to use a double to communicate with your partner and interfere with the opponents. We'll also cover much more about your role as advancer, when your partner makes a takeout double.
Note that Negative Doubles are part of the Competitive Bidding course, lesson 4.