Here is a list of all files with brief descriptions:

src
pulse
channelmap.h	Constants and routines for channel mapping handling
context.h	Connection contexts for asynchronous communication with a server
def.h	Global definitions
direction.h	Utility functions for pa_direction_t
error.h	Error management
ext-device-manager.h	Routines for controlling module-device-manager
ext-device-restore.h	Routines for controlling module-device-restore
ext-stream-restore.h	Routines for controlling module-stream-restore
format.h	Utility functions for handling a stream or sink format
gccmacro.h	GCC attribute macros
glib-mainloop.h	GLIB main loop support
introspect.h	Routines for daemon introspection
mainloop-api.h	Main loop abstraction layer
mainloop-signal.h	UNIX signal support for main loops
mainloop.h	A minimal main loop implementation based on the C library's poll() function
operation.h	Asynchronous operations
proplist.h	Property list constants and functions
pulseaudio.h	Include all libpulse header files at once
rtclock.h	Monotonic clock utilities
sample.h	Constants and routines for sample type handling
scache.h	All sample cache related routines
simple.h	A simple but limited synchronous playback and recording API
stream.h	Audio streams for input, output and sample upload
subscribe.h	Daemon introspection event subscription subsystem
thread-mainloop.h	A thread based event loop implementation based on pa_mainloop
timeval.h	Utility functions for handling timeval calculations
utf8.h	UTF-8 validation functions
util.h	Assorted utility functions
volume.h	Constants and routines for volume handling
xmalloc.h	Memory allocation functions