If you're an avid twitter user, you will know that twitter wants your experience tailored to you. For example, the trending topics section of twitter can be adjusted from nearby locations, to tailored trends. Even the ads that twitter displays on your timeline are tailored. Everything about twitter is personal and twitter plans on making this "tailored experience" even better by tracking your apps. Now this may sound a little nosey of them to do so and also an invasion of privacy, but twitter does not plan on collecting information inside of the apps you use. According to twitter, this new feature is called App Graph, and with this new addition they want to create a list of apps that you have installed on your device. By doing this, twitter can better display ads, make improvements to there "who to follow" suggestions, and show more relevant promoted content.
Why is twitter doing all of this other than trying to make the experience more personal to you? Well its simple, to make more money. Tons of websites rely on ads to build revenue. Some sites do it better than others and in twitters case, they are doing it way better. Instead of just showing you random ads that you have no interest in, they want to show you stuff that you have like and enjoy. Now instead of being irritated of seeing ads that you have no interest in such as toms bug repellent, you will now be shown stuff that you enjoy like Android or Hello Kitty. Okay, those may be poor examples but the point is, you're going to be less reluctant to exit twitter because of annoying "Who To Follow" suggestions and ads that don't mean a hill of beans to you.
Now if you are one of those people that wish for twitter to not collect a list of apps on your device, you have the option to opt out. In the next update for twitter you will be prompted to choose whether or not you want twitter to track your apps. If you miss that, you can always click on the overflow icon, go to your settings, tap on the account you want to adjust, and under the other tab, you can adjust the settings to Tailor Twitter based on my apps. With this option you're not tied down to twitter knowing what you have on your phone.