Is there a difference between unpaid internships and paid internships?

No, they both are helpful to gain experience and it's always a plus to get paid while learning.

It's less about skill level or effort put in and more about industry. It's standard to do unpaid internships in the govt sector, for non-profits, for highly competitive newspapers or media companies, social work, teaching, etc. In these spaces it's just not expected to have to pay due to lower operating budgets or more demand than supply. In the corporate, tech, and STEM world, there's often more money allotted to recruit new candidates and these companies are competing against each other to get the top talent so they're more likely to pay.

You can get great experience at a paid or unpaid internship, and future jobs you applied to will never even ask if you were paid or not. It's more about the experiences you gain and the skills you can showcase and talk to later, with any internship you have.

Being paid in internships is just a form of compensation and encouragement to the student, it is not mandatory. that should answer your question