[Docs] Fix docs about embedding overhead (#20529)

fixes #20501

Author: kripken

site/source/docs/porting/files/packaging_files.rst

@@ -6,7 +6,11 @@ Packaging Files
 
 This topic shows how to package the files that will be used to populate :ref:`Emscripten's virtual file system <file-system-overview>` when the page is loaded.
 
-There are two alternatives for how files are packaged: *preloading* and *embedding*. Embedding puts the specified files inside the generated JavaScript, while preloading packages the files separately. Embedding files is much less efficient than preloading and should only be used when packaging small numbers of small files. Preloading also enables the option to separately host the data.
+There are two alternatives for how files are packaged: *preloading* and
+*embedding*. Embedding stores the specified files inside the wasm file, while
+preloading packages them in a bundle on the side. Embedding files is more
+efficient than preloading because there isn't a separate file to download and
+copy, but preloading enables the option to separately host the data.
 
 *Emcc* uses the *file packager* to package the files and generate the :ref:`File System API <Filesystem-API>` calls that create and load the file system at run time. While *Emcc* is the recommended tool for packaging, there are cases where it can make sense to run the *file packager* manually.