Ussualy they collect device information such as make, model, OS, MAC Address and the browsing history. Also they can track social media information if you login

Ussualy they collect device information such as make, model, OS, MAC Address and the browsing history. Also they can track social media information if you login with your google/facebook account. They may use this information for marketing and advertising purposes, or sell it to Advertising companies, Third-Party Analytics Companies or even Government Authorities.