But what function?
An icon library is file containing one of more icons and their names. Because the file format of an icon library is the same a file format of an ordinary .dll file, Windows is able to use icons directly from the icon library (You can say that an .icl file is just a renamed .dll file with some restrictions).
.icl files usually only contain icons and no other resources (like cursors, etc.). Also, .icl files optionally have a custom resource block with user friendly icon names.
Because there are two formats for .dll files (16-bit and 32-bit), there are also 2 formats of .icl files. 16-bit .icl files are legacy of Windows 3.11 and are not generally supported anymore.
Because .icl is a renamed .dll, it follows its rules for identifying icons. Each icon has a numerical (0-32767) or a text identifier. Beside that identifier, each icon also has a language code. Each combination of the identifier and the language code can only be used once in an icon library.
.icl files may also contain user friendly names. Because the format of the names is not standardized, there may be problems using non-English characters or empty descriptions when using the .icl files in icon editors.
RealWorld Icon Editor can read 16-bit and 32-bit .icl files and writes always 32-bit .icl files.
But what function?
You cannot extract icon names with that function. Icons names are saved in a optional, non-standard resource block.
how do i create an icon library with realworld
Double-click "New icon library" on the Create page.
can i use only 32 bit (128x128, 48x48, 32x32, etc...) icon files?
do i need 24 bit or 16 bit?
24bit are very unusual and not recommended, 16bit is not valid for icons; so basically yes, just 32bits is fine these days
I have no idea where to look to find my comment... I will look back
here periodically for yours...