Symbols beginning with system-specific local label prefixes, typically .L for ELF systems or L for traditional a.out systems, are called local symbols. See Symbol Names. Normally you do not see such symbols when debugging, because they are intended for the use of programs (like compilers) that compose assembler programs, not for your notice. Normally both
ld discard such symbols, so you do not normally debug with them.
This option tells
as to retain those local symbols in the object file. Usually if you do this you also tell the linker
ld to preserve those symbols.