Great question! The good news is you don’t have to know right now! Think about what you like to do, research a day in the life, explore internships, talk to people who are already working in a specific field, take classes around subjects that you are interested in. I thought I wanted to be a journalist - I did a 3 month internship & found out it wasn’t for me. But I had been in the hospitality business for years & realized I really like working with customers after taking some time away from it. I then got a job as a customer service rep & loved it right out of college.
Lots of people change jobs and even career paths every 2-5 years. Obviously if you train to be a neurosurgeon, you would not be hopping around like that. But, let's say you start out in customer service at a call center for a top airline. You are good. You move into training, for the same company, Then you go into training at a hotel. You work towards doing their Event Planning, hosting big parties and conventions. You are good at it. Then you go into sales, where you are actually out trying to get people to hold conventions at your hotel. Then you become a corporate trainer for the hotel sales team.
What you do is look at your transferable skills - experience at one job that relates to another. People get pretty creative with this. As long as you believe you can do it, and you can show how that experience relates, you can keep right on moving!
You are right to be skeptical of things you haven't done. Some jobs have a down-side, that people rarely discuss. Keep asking questions, especially if there are particular jobs you want to explore!
So I struggled with this very early in my adult life. I still struggle with it. Ultimately, In my own opinion, think about what you like to do. If you didn't have to work for a living, how would you spend your days? Whatever that answer is...find a field tied to it. Also, as others have mentioned....there are many steps to career progression. Just do your best at whatever you are doing and make the most of it and have an open attitude.