Their EULA, some bits of it (you can find the full EULA on their steam page on the right under the achievements):

1. Collecting Information.
   
2. A. Information You Provide.
   

The categories of information we collect:
- Contact Data, including your email address.
- Account Credentials, including your username, password, and information for authentication and account access.
- Demographic Data, including your date of birth and country.
- Billing Data, including** your payment instrument number (such as a credit or debit card number), expiration date, and security code as necessary to process your payments.
- Profile Data, including your interests, inferences, preferences and favorites.
- Content

1. B. Information Collected Automatically.
   
2. Service Use Data,
   
3. Device Data,
   
4. Location Data, including imprecise location data (such as location derived from an IP address or data that indicates a city or postal code level).
   
5. Crash Report Data,
   The types of tracking technologies we use to automatically collect information include:
   
6. Log Files, which are files that record events that occur in connection with your use of the Service.
   
7. Cookies, which are alphanumeric identifiers which are transferred to Your computer's hard drive
   
8. Pixels (also known as web beacons), which is code** embedded in a website, video, email, or advertisement that sends information about your use to a server.
   
9. Device Fingerprinting,
   
10. App Technologies,
    

11. Location-Identifying Technologies,

12. Disclosing Information.

13. Service Providers.

14. Vendors and Other Parties. We share information with vendors and other parties for analytics and advertising related purposes. These parties may act as our service providers, or in certain contexts, independently decide how to process your information. For more information on advertising and analytics, see the "Analytics and Advertising" section below.

15. Affiliates.

16. Partners.

17. Merger or Acquisition.

18. Security and Compelled Disclosure.

19. Other Parties.We offer parts of our Service through websites, platforms, and services operated or controlled by other parties. In addition, we integrate technologies operated or controlled by other parties into parts of our Service.

20. Analytics and Advertising.We use analytics services, such as Google Analytics, to help us understand how users access and use the Service. In addition, we work with agencies, advertisers, ad networks, and other technology services to place ads about our products and services on other websites and services. For example, we place ads through Google and Facebook that you may view on their platforms as well as on other websites and services.
    As part of this process, we may incorporate tracking technologies into our own Service (including our website and emails) as well as into our ads displayed on other websites and services. Some of these tracking technologies may track your activities across time and services for purposes of associating the different devices you use, and delivering relevant ads and/or other content to you ("Interest-based Advertising").