Here is a list of all files with brief descriptions:

include
librealsense2
h
rs_advanced_mode_command.h	Advanced Mode Commands header file
rs_composite_option.h	Generic entry points shared by every composite (multi-field, atomically-exchanged) XU control. A separate identity space from rs2_option, keyed by rs2_composite_option_id. Each call below is exactly one UVC transaction: all fields of the option's payload travel together, atomically
rs_config.h
rs_context.h	Exposes RealSense context functionality for C compilers
rs_decimation_filter_dpp.h	Cast-target struct for RS2_COMPOSITE_OPTION_DECIMATION_FILTER_DPP (see rs_composite_option.h). Same shared HKR DPP wire layout (see rs_hdrd_control.h): dpp_header + 8 int32 param slots, 2 used (38 bytes, little-endian, pack(1)); ctl_id = 0x0001
rs_device.h	Exposes RealSense device functionality for C compilers
rs_dpp_header.h	Wire header shared by every control in the HKR Depth Post-Processing (DPP) composite-option family: this header + a fixed 8-slot int32 param block; param_count says how many are active, the rest MUST be zero on SET. See rs_hdrd_control.h for a control that uses it
rs_eth_config.h	Exposes RealSense ethernet configuration functionality for C compilers
rs_frame.h	Exposes RealSense frame functionality for C compilers
rs_hdrd_control.h	Cast-target struct for RS2_COMPOSITE_OPTION_HDRD_CONTROL (see rs_composite_option.h). Wire layout: dpp_header + 8 int32 param slots, 7 used (38 bytes, little-endian, pack(1)); ctl_id = 0x0008. Open item: activates at 720p/960p only - resolution-gating not yet encoded here
rs_internal.h	Exposes RealSense internal functionality for C compilers
rs_option.h	Exposes sensor options functionality for C compilers
rs_pipeline.h	Exposes RealSense processing-block functionality for C compilers
rs_processing.h	Exposes RealSense processing-block functionality for C compilers
rs_record_playback.h	Exposes record and playback functionality for C compilers
rs_rum.h	Exposes RUM (Real User Monitoring) functionality for C compilers
rs_safety_sensor.h	Exposes RealSense safety sensor functionality for C compilers
rs_sensor.h	Exposes RealSense sensor functionality for C compilers
rs_temporal_filter_dpp.h	Cast-target struct for RS2_COMPOSITE_OPTION_TEMPORAL_FILTER_DPP (see rs_composite_option.h). Same shared HKR DPP wire layout (see rs_hdrd_control.h): dpp_header + 8 int32 param slots, 4 used (38 bytes, little-endian, pack(1)); ctl_id = 0x0002
rs_types.h	Exposes RealSense structs
hpp
rs_context.hpp
rs_device.hpp
rs_eth_config.hpp
rs_export.hpp
rs_frame.hpp
rs_internal.hpp
rs_options.hpp
rs_pipeline.hpp
rs_processing.hpp
rs_record_playback.hpp
rs_rum.hpp
rs_safety_sensor.hpp
rs_sensor.hpp
rs_serializable_device.hpp
rs_types.hpp
rs.h	Exposes librealsense functionality for C compilers
rs.hpp
rs_advanced_mode.h
rs_advanced_mode.hpp
rsutil.h
librealsense2-gl
rs_processing_gl.h	Exposes RealSense processing-block functionality for GPU for C compilers
rs_processing_gl.hpp