luac is the Lua compiler.
It translates programs written in the Lua programming language
into binary files containing precompiled chunks
that can be later loaded and executed.
The main advantages of precompiling chunks are:
protecting source code from accidental user changes,
off-line syntax checking.
Precompiling does not imply faster execution
because in Lua chunks are always compiled into bytecodes before being executed.
luac simply allows those bytecodes to be saved in a file for later execution.
Precompiled chunks are not necessarily smaller than the corresponding source.
The main goal in precompiling is faster loading.
In the command line,
you can mix
text files containing Lua source and
binary files containing precompiled chunks.
luac produces a single output file containing the combined bytecodes
for all files given.
Executing the combined file is equivalent to executing the given files.
the output file is named
luac.out, but you can change this with the
Precompiled chunks are
not portable across different architectures.
the internal format of precompiled chunks
is likely to change when a new version of Lua is released.
Make sure you save the source files of all Lua programs that you precompile.