What does it mean "by the way"?

English as a Second Language English Vocabulary, Grammar and Idioms
1

hi
what does it mean " by the way " ?
also pine down ?

2

“By the way” is used to introduce a new topic, although one that is related to the first.
“Pipe down” means “be quiet” and is not very polite.

3

thanks a lot :slight_smile:

4

MW gives it as:

by the way : by way of interjection or digression : incidentally