This is an auxiliary template allowing one to encode "
|" within template parameters. It is not necessary to use a "
|" in these cases; it is better use "
|" for this purpose. However the "
|" delimiter for a Wiki table has to be escaped by a template if it is used within a template. See Template:Babel for an example of usage.
Note that there is no such problem with "
!" (exclamation point); it only affects "
|" (vertical bar) in conjunction with the parameter default mechanism within tables.