ex ‧ plan ‧ a ‧ to ‧ ry /ɪkˈsplænət ə ri $ -tɔːri/ BrE AmE adjective
[ Word Family: adjective : ↑ unexplained , ↑ explanatory , ↑ explicable ≠ ↑ inexplicable ; noun : explaining, ↑ explanation ; verb : ↑ explain ; adverb : ↑ inexplicably ]
giving information about something or describing how something works, in order to make it easier to understand:
There are explanatory notes at the end of each chapter.
⇨ ↑ self-explanatory