A retreat is the classic format in yoga practice for going really deep and challenging the comfort zone and habitual patterns that the ego has built around it.
As I understand it, a retreat involves at least six hours of daily practice and is conducted in a residential setting, away from home and the roles and patterns we often fall into and are constrained by.
In a way, retreats are a deeper form of workshop / immersion and, in my experience, a very powerful tool for transformation. Like workshops, they can focus on specific areas of practice or topics and are a fantastic creative opportunity for any teacher to deliver the teachings and provide a safe space that allows students to immerse themselves deeply. The duration of a retreat can vary from a long weekend to several weeks.
Another aspect I enjoy is the relaxed environment (unlike teacher trainings, there are no benchmarks and tests here) and actually taking people to places like India and Bali that are steeped in yoga culture . But just “getting out of the rut” in your own country for a while and practicing deeply is fantastic.