Later on I will tell you what later means. :P Intuitively speaking, 'later on' somehow suggests that something will happen in the not too distant future. With the usage of 'later' the length of time is indeterminable.

later on = adverb only I'll do it later on. Nowadays we just say "later". later = adjective. But see its additional use above. Geddit? 分かったかな。

same thing