University is kind of like when you go to school, but it's even bigger and harder. To get into university, you usually have to apply and give lots of information about yourself. Then, the university will decide if they want to let you join.
At university, you don't just have classes like you do in a regular school; you take classes that are related to a subject or field that you're interested in. For example, if you're interested in being a doctor, you'll take classes in subjects like biology and chemistry.
Once you finish all the classes that you need to take, you usually have to do a big project or take an exam to prove that you know a lot about the subject that you've been learning about. If you pass this final test, then you will get a degree. A degree is like a certificate that shows that you know a lot about the subject.
Once you have a degree, you can use it to help you get a job in your field or to continue studying another subject. So, university helps you to gain more knowledge so that you can get a better job or continue your studies after you finish.