Digression
WordNet
noun
(1) Wandering from the main path of a journey
(2) A turning aside (of your course or attention or concern)
"A diversion from the main highway"
"A digression into irrelevant details"
"A deflection from his goal"
(3) A message that departs from the main subject
WiktionaryText
Noun
- A departure from the subject, course, or idea at hand; an exploration of a different or unrelated concern.
- The lectures included lengthy digressions on topics ranging from the professor's dog to the meaning of life.