I hear students talking about 'jihad' and about a 'Caliphate'. Does this mean that they are radicals and I should be concerned?

Not necessarily. It is true that most people who hold views that others might consider 'extremist' or 'radical' are particularly interested in 'jihad', when interpreted as involving violent action. However, jihad is an extremely broad concept and is a strongly positive idea in Islam; the Arabic word jihad means 'to struggle' or 'to exert oneself'. It is to be expected that Muslims will take it very seriously.

Similarly, the avowed aim of some groups labelled 'extremist' or 'radical' is to establish a Caliphate, an Islamic form of government, and thus heightened interest around that concept might be a feature of those who are attracted to such ideas. However, the Caliphate is a central idea in Islamic history and political thinking, as well as a point of contemporary debate amongst Muslims today. What is of importance in assessing such discussion is whether or not people show the willingness to achieve social and political aims solely within the bounds of commonly-accepted Islamic ethical principles.