Olympus ZOOM 105 DLX - Manual (Page 34)

When you want to fire the flash every shot.
In the FILL-IN Flash mode, the flash fires regardless of
available light. For example, this mode can be used to
brighten up a subject's shaded face or under artificial
lighting such as back-lit, fluorescent light. Use this
mode within the flash working range (p. 31).
It may be hard to work under the excessively bright
light.
34
FILL-IN (Forced Activation)