Here is a list of all documented files with brief descriptions:

core
math
controls
bang_bang.h	A control loop that utilizes only the positive error to get an output value
feedback.h	A pure virual class to function as an interface for all feedback control loops
feedforward.h	A pure virual class to function as an interface for all feedforward control systems
linear_motor_ff.h	A control loop that uses static friction, velocity, and acceleration to get an output voltage
linear_plant_inversion_ff.h	A control system that uses inverted discrete plant dynamics to get an output value
linear_quadratic_regulator.h	A control loop that uses current states, reference states, and cost matrices to find an optimal gain matrix as an output
pid.h	A control loop that utilizes the proportional, integral, and derivative values of error to get an output value
estimator
kalman_filter.h
unscented_kalman_filter.h
geometry
point2d.h
pose2d.h
rotation2d.h
transform2d.h
translation2d.h
twist2d.h
kinematics
chassis_accelerations.h
chassis_velocities.h
tank_kinematics.h
tank_wheel_accelerations.h
tank_wheel_velocities.h
numerical
numerical_integration.h
spline
cubic_hermite_spline.h
hermite_point.h
quintic_hermite_spline.h
spline_base.h
spline_path.h
systems
dare_solver.h
discretization.h
linear_system.h
trajectory
constraints
centripetal_acceleration_constraint.h
max_velocity_constraint.h
rectangular_region_constraint.h
tank_kinematics_constraint.h
tank_voltage_constraint.h
trajectory_constraint.h
trajectory.h
trajectory_config.h
trajectory_generator.h
trajectory_parameterizer.h
eigen_interface.h
moving_average.h
spline.h
units.h
util.h
core.h	The main header for the Core package, which handles all architecture-independent functionality, like math and controls
crust
devices
device.h	Implements device port and connection logic used by VEX device subclasses
rotation.h	V5 rotation sensor using Core's geometry and physical units
crust.h	The main header for the Crust package, which serves as Brick's very own VEX V5 runtime
v5rt.h	The header for the VEX V5 C SDK
mantle
mantle.h	The main header for the Mantle package, which handles higher-level robotics mechanisms