Durham is a collegiate university rather than a campus university. This means that students are all placed in colleges which provide everything from room and board, to student support, to societies and more. There is also university wide support, but the colleges create smaller communities in the middle of a very large university.
Since colleges are smaller than the whole university they often can provide more specialised help and support to students. They also provide a social space for students to engage with both in terms of actual rooms as well as with clubs, societies, and athletics. Colleges also can work with a student’s department if there are any health issues or outstanding circumstances. Basically you can think of your college as your home and your family while you are a student at Durham as they will seek to do their best to make sure you are successful personally and academically.
You can find a lot more information on our colleges here.