This will vary from school-to-school, but typically, alongside the core subjects (English, Maths and Science), students are introduced to a whole range of subjects. They are very likely to be taught at least one modern foreign language, get their hands dirty with Design & Technology, explore various Humanities subjects and get their creative juices flowing with Music and the Arts.
At most schools, students will need to select which GCSE options to choose near the end of Year 9 (in some cases, even earlier!) and so, getting a genuine feel of the various subjects on offer can help them make more informed decisions.  Being taught a subject by an expert who is truly passionate about it can make all the difference in cultivating a genuine appetite to pursue that subject at GCSE level and beyond.