It's a very good question in light of what my very talented colleague, Dr. Perry, just presented.
If we think of this as a pyramid, at the top we have people who are engaged in illegal action and violent action. Those are the people we commonly refer to as terrorists. Below that, we have people we refer to as radicals, who are engaged in possibly one or more forms of illegal actions, whether they are an illegal protest, perhaps firearms violations, or so forth, but they're not violent per se against third parties or the public. Below that, you have activists. Those are people who, for instance, might possibly sympathize with radicals or with terrorists, but they aren't engaging in forms of illegal action, illegal speech, incitement, hate and the like.
We often conflate these in public discourse, and I think it's important for intelligence, for enforcement purposes and for policy purposes to treat these as three distinct problems. One might be a problem of counter-radicalization, persuading people. One might be a problem of making sure we have the right incentives in place so that people who might be engaged in illegal action don't engage in violent action, and for those who are predisposed or engaging in violent action, make sure we have the criminal intelligence capabilities to detect and disrupt those before they can do harm.