Try this example:
This is the abstract.
This are the acknowledgements.
This is an appendix.
Then, change the line
and see what happens: all names have changed because
llncs redefines them for French language.
As you can see, loading the
llncs class with the option
francais (you can also use the option
deutsch to switch to German) all the names are switched to French.
Also note that this class doesn't define any predefined command for using
\ackname. You have to load packages that use these names for exploiting them somehow.