The change in environment going from secondary school to University can be quite daunting. You're instantly in a new location, surrounded by a great number of people from all walks of life and have to adjust to a completely new schedule than you're used to. Here are some things you can expect when transitioning into University.
In school you may be used to going into class with one teacher and, depending on the subject, a handful of students. Lectures have a different structure to school classes. In lectures you're given information usually through a presentation and you're expected to take notes in the way you want. Typically the lecture will be pre-uploaded on your Uni's portal, so you can sign in to your account and follow along on your own device. The pace of the lecture can be quite fast, and there can be a lot of people in the room so don't expect a lot of questions to be asked or answered during the presentation. That being said, it's important to skim through the material prior to the lecture so you have an idea of what is going to be covered; go over the content post-lecture if you didn't understand anything or approach the lecturer if they're available during a break or after the lecture. Most lectures now are also recorded and uploaded incase you miss a lecture or want to go through it again.
Seminars are a great place to have questions answered and get practise on the content that's being covered. For most Universities, seminars are used to give practise questions for students to work through and get feedback on their understanding. It's a nice change of pace from all the lectures that you attend and very useful if you keep up to date with everything being covered.
University is a place full of people from all over the world, pursuing all sorts of degrees. You can meet a lot of new people by joining clubs/societies based on your interests. There are sports teams you can join, societies like photography or debating, academic or enterprise societies like the finance society, or learn about other cultures by joining a cultural society like the Korean or Russian society. Each Uni is slightly different in which societies they offer which you can always find on their website. Societies and clubs are a great way to meet new people outside of your course and grow your social circle with people that share your interests and/or culture.
Though University can intimidating when you first start it, only takes a few weeks to adjust to the new environment. The Uni you go to has a lot to offer and it's important to take advantage of all the opportunities. More importantly, make sure to enjoy your time there!