[This is preliminary documentation and subject to change.]
The Help property, retrieved by calling the IAccessible::get_accHelp method, can provide information that tells the user about the object's function. For example, the Help property for a toolbar button that shows a printer might be, "Prints the current document." This text is not always unique within the user interface; it acts purely to elaborate on the object's purpose and what actions it might perform.
Not all objects support the Help property; if the call to get_accHelp returns the DISP_E_MEMBERNOTFOUND value, then the object does not support this property.