Using Parental Controls, parents and guardians can determine which
software and Channels can be used and downloaded and which games can be
played based on the game's rating. They can also manage the number of
Wii Points that can be used by their children or other household
members.

If you apply Parental Controls, you will be prompted to set a 4-digit
PIN which will allow you to adjust the Parental Controls settings in
the future and also allow you to access content that may be restricted
by the Parental Controls settings.

Please note, the Parental Controls default setting is "OFF" which means
that the console will allow all content unless you change the settings.
There is one Parental Controls setting per console, so it is
recommended that you put the settings on the most secure that you need
for your family; you can then share the PIN with users who may be
allowed access to blocked content.

Please see
p. 46 in the Wii Settings and Data Management section of the Wii Operations Manual (Channels and Settings).