Scroll down to Personalization and Data and click Edit. You can enable or disable the following settings according to your wish.
Personalized ads — If you turn on this, users will see interest-based ads on and off Twitter.
Personalization based on apps — This shows the personalized ads and content based on the apps you've installed on your phone.
Personalization across devices — If you turn on this, the micro-blogging site will display ads, content, and users to follow in mobile based on the sites you have visited in your PC or laptop.
Personalization based on the places you’ve been — Personalized ads and content based on your current or previous locations.
While Twitter gained lots of criticism for this, users can easily disable all personalization and access to data. In order to do that, go to Personalization settings and click the Disable All at the top right corner of the page.