It will include, most importantly, teaching practice: on an IHC or a CELTA you have to teach. And you teach real students, you don’t teach your colleagues, you don’t teach people who are pretending to learn English; you teach genuine learners of English and you’re observed doing that, and you receive feedback.
You’re with a group of people with the same objectives. You’re with six or 10 or 12 people who are all interested in developing as teachers, and that’s a really important element of the course. A successful IHC or a successful CELTA is one where the candidates support each other.