They basically explain all about the job roles and such as expected and usually have a warm up activity such as asking applicants to form small groups of two/three (depending on group size) and they ask for each to find out several facts about their life such as what they are studying and if they have pets etc. Then they have a main activity were they assess your behaviour and any skills you have. I did one were I had to pick a product and explain its benefits and why people would buy it, also another one were I had to try and create a speech to sell the product.