This is a question specific to France.
Permanent positions at the university typically are either research only or research and teaching. For the latter, positions are "maître de conférences" (assistant professor) and "professeur des universités" (full professor). In both cases, you are affiliated to one (or two) disciplinar "sections" listed here. Several are related to physics : 28, 29, 30, 60...
However, there exists other permanent positions called "physicien" (physicist), which belong to a different, separate "corps", see here.
How is that so and what is the difference ?