The Miocene was the first epoch of the Neogene period (23-2.5 million years ago), followed by the much shorter Pliocene epoch (5-2.6 million years ago); both the Neogene and Miocene are themselves subdivisions of the Cenozoic Era (65 million years ago to the present). Climate and geography.
The dictionary meaning of the word Digress is 'to leave the main subject temporarily in speech or writing.' or simply deviate. As you say,I digress means  I am straying from the main subject right now. . Like in this sentence - 'I need to digress a bit to let the ink dry.'. Hope this helps :)
A buttress is an architectural structure built against or projecting from a wall which serves to support or reinforce the wall.[1] Buttresses are fairly common on more ancient buildings, as a means of providing support to act against the lateral (sideways) forces arising out of the roof structures that lack adequate bracing. The term counterfort can be synonymous with buttress, and is often used when referring to dams, retaining walls and other structures holding back earth.