Comments on some movement functions

Marlin/Marlin_main.cpp

   }
   feedrate = homing_feedrate[axis] / hbd;
 }
+//
+// line_to_current_position
+// Move the planner to the current position from wherever it last moved
+// (or from wherever it has been told it is located).
+//
 inline void line_to_current_position() {
   plan_buffer_line(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS], feedrate / 60, active_extruder);
 }
 inline void line_to_z(float zPosition) {
   plan_buffer_line(current_position[X_AXIS], current_position[Y_AXIS], zPosition, current_position[E_AXIS], feedrate / 60, active_extruder);
 }
+//
+// line_to_destination
+// Move the planner, not necessarily synced with current_position
+//
 inline void line_to_destination(float mm_m) {
   plan_buffer_line(destination[X_AXIS], destination[Y_AXIS], destination[Z_AXIS], destination[E_AXIS], mm_m / 60, active_extruder);
 }
 inline void line_to_destination() {
   line_to_destination(feedrate);
 }
+/**
+ * sync_plan_position
+ * Set planner / stepper positions to the cartesian current_position.
+ * The stepper code translates these coordinates into step units.
+ * Allows translation between steps and units (mm) for cartesian & core robots
+ */
 inline void sync_plan_position() {
   #if ENABLED(DEBUG_LEVELING_FEATURE)
     if (DEBUGGING(LEVELING)) DEBUG_POS("sync_plan_position", current_position);