What Does MUI_RESERVEFILE_LANGDLL Do?

I did not find documentation for this in Help, Wiki, or forums. Would like to understand what this macro does.

from the MUI docs:

If you want the installer to display a language selection dialog (have a look at the MultiLanguage.nsi example), insert the MUI_LANGDLL_DISPLAY macro in the .onInit function:

EDIT:
oops, wrong function... 🤨

Looking at the docs, it appears that it simply reserves the files needed for the language selection dialog. There's a small blurb about it under section 6 ("Reserve Files") of the MUI docs

I was able to figure out what the MUI_LANGDLL_DISPLAY macro does. The MUI_RESERVEFILE_LANGDLL remained a mystery. MUI docs? I have been using the NSIS user manual thinking it would be explained there.

I read chapter 6 of MUI docs. It seems that these "RESERVE" macros preload files into memory for faster execution? This explains why it seems not to be a make-or-break option as i noticed in a couple other forum postings. If someone can confirm than this clears things up. I was just curious. Like to know what i am doing (or pretend to)!

MUI options are explained in the MUI help file. There is a link for it on the main NSIS menu included with the installation. (Or browse for it at ${NSISDIR}\Docs\Modern UI\readme.html

The reserve function moves the files to the beginning of the installation's data block to allow it to be extracted first which improves load time.

The ReserveFile function is explained better in the NSIS help files.