What is the difference between doing a PhD in a research lab outside a University campus and doing PhD in a lab inside a University campus?

The practicalities of doing a Ph.D. in a research lab outside a University versus doing one in it are quite similar. In either case, the student has to register with a University since they are the ones who grant the Ph.D. degree. For example, though I did my Ph.D. in a research lab run by the Indian Council of Medical Research, I was registered for the degree with the local medical university. However, the university played no role in the day-to-day management of my degree. They only figured towards the end by managing the process of my thesis examination, sending my thesis to outside examiners and helping conduct my viva-voce ('by live voice') exam.

The Ph.D. experience in a research lab is certainly quite different from one in an university. In the former, the Ph.D. student is in the midst of research lab employees and is typically among the junior-most members in the lab. In the latter, surrounded by other students many of whom are pursuing Bachelor's and Master's, the Ph.D. student isn't typically the junior-most. A research lab Ph.D. also typically works on their research project from day one all the way through. No course work.

So more of a work-like experience for a research lab Ph.D. student compared to a university student-like experience for a university Ph.D. student.

https://www.quora.com/What-is-the-difference-between-doing-a-PhD-in-a-research-lab-outside-a-University-campus-and-doing-PhD-in-a-lab-inside-a-University-campus/answer/Tirumalai-Kamala