These are places where avalanches are commonly triggered. They are generally places where the snowpack is weaker, already under stress and overloaded. These areas should be avoided if possible.
These are rollovers where the slope angle increases. If you are standing at the top of a slope and cannot see the bottom as it rolls away from you, then this is a convexity. Like the outside shape of a beach ball.
These slopes have little to hold them up from below
In the picture below, the whole snowpack has slid as one large slab exposing the ground. This is more typical in springtime. The slope is steep and unsupported.
The slab avalanches have broken away from one rocky outcrop to another in the photos below. These are weak points. They are like holes in the snowpack, so any strength the snowpack might have is less at these points.
Slopes facing south will remain colder, new snow takes longer to stabilise, and weak layers can last longer.
Slopes overloaded with windblown snow are under tremendous stress due to the extra weight sitting on them. Weak layers will often fracture naturally.