Makefile and Kconfig

make file

Define the files to be built and and link to other files,  Makefiles within the kernel are kbuild Makefiles that use the kbuild infrastructure, these make  evaluates to either y (for built-in) or m (for module) If it is neither y nor m, then the file will not be compiled nor linked.

https://www.kernel.org/doc/Documentation/kbuild/makefiles.txt

Kconfig

Every entry has its own dependencies. These dependencies are used
to determine the visibility of an entry. Any child entry is only
visible if its parent entry is also visible.

Menu entries
------------

Most entries define a config option; all other entries help to organize
them. A single configuration option is defined like this:

config MODVERSIONS
bool "Set version information on all module symbols"
depends on MODULES
help
 Usually, modules have to be recompiled whenever you switch to a new kernel.

Every line starts with a key word and can be followed by multiple
arguments.  "config" starts a new config entry. The following lines
define attributes for this config option. Attributes can be the type of
the config option, input prompt, dependencies, help text and default
values. A config option can be defined multiple times with the same
name, but every definition can have only a single input prompt and the
type must not conflict.

https://www.kernel.org/doc/Documentation/kbuild/kconfig-language.txt