Do you mean the sections that teachers can add in the course settings,
or the sections that get added by the school?
They should be mostly the same.
If I have ENGLISH 101 that meets at a certain time, and another
ENGLISH 101 that meets at another time, then I would have 2 sections
of ENGLISH 101. Also, I could have 2 sections that are actually the
same class, such as SocialWork 101 and Psychology 105. These meet at
the same time, same teacher, same classroom, etc. These 2 courses
would then be what's called cross listed, or xlisted, in Canvas. One
Canvas page would contain all students in SW 101 and PSYCH 105, the
teacher would then just edit one place in Canvas.