Consider magical darkness like that created by the Darkness spell or by the Darkmantle creature's Darkness Aura. Both say that mundane (natural) light can't illuminate its darkness and that their darkness will dispel any spell of 2nd level or lower whose illumination overlaps it.
Now consider carrying a light source toward a 5-foot-wide wall of magical darkness. If it's a 2nd-level (or lower) source of magical light, the source will be dispelled the moment its lit area touches the wall. However, if it's a mundane light source like a lit torch, some interesting effects may arise:
If the torch is close to the wall of magical darkness, will its light still somehow penetrate that darkness to illuminate the space on the wall's opposite side?
If the torch is brought into the wall, will it remain lit?
If yes, will that torch inside the wall still illuminate its usual regions outside the wall, similar to #1?
Or, restated: can mundane light penetrate magical darkness to illuminate regions outside the magically darkened space? And can a mundane light source remain lit when inside magical darkness?