Whitening? Reversing/eliminating gingivitis? Freshening your breath? How does it all work?
If you read the fine-print on ANY toothpaste that you choose to buy, the instructions say to use twice daily. So if you want white teeth, use twice daily. Want to reduce your gingivitis? Use twice daily.
However, the trick is that almost any toothpaste you use twice daily will do these things. Brushing the stain off your teeth twice (or more) per day will generally make & keep them whiter, while also keeping bacteria away from your gums. When the bacteria is kept away from your gums, they are generally healthier and you will have less gingivitis. I wouldn't necessarily buy into the claims the brand is making - decide based on how much YOU like the product, not what it promises to do for you.
Sensitivity toothpaste is a different story - it has different ingredients than whitening toothpaste. There aren't a ton of sensitivity products out there, my advice is to try them out and go with what you like best and feel is working best.
A great example of advertising is Crest's new "Gum Detoxify" toothpaste. I am on the fence about the ability to clean below the gums and reverse gingivitis (any more than other toothpastes do). Let's wait for some independent research and then we'll see.
That being said, I have recently tried it - and I love it! I feel that it has decreased my sensitivity, and it leaves a very nice, fresh taste after brushing. We have recently started carrying sample sizes of this toothpaste at the office- make sure to ask for one when you come in!