When you want to build and experiment with x86 (32-bit) based binaries on an x64 based linux kernel. This is often useful for reverse engineering and exploit proof of concepts, as x86 offers a number of simplicities over x64.

On Kali add overall subsystem support with:

dpkg --add-architecture i386

Then to get a working development environment:

apt update
apt install libc-dev-i386-cross gdb-multiarch execstack gdb-peda lib32tinfo6 lib32ncurses6 lib32ncurses-dev gcc-7

You should be good to start compiling for an x86 target. Make sure to add -m32 to any CFLAGS and LDFLAGS parameters in the Makefile.

TODO: add working example