A discourse marker meaning 'by the way' or 'incidentally' used to change the subject or add a remark.
ところで、明日の会議は何時からですか？
By the way, what time does tomorrow's meeting start?
旅行は楽しかった。ところで、写真はもう見た？
The trip was fun. By the way, have you seen the photos yet?
ところで、最近何か面白い本を読んだ？
By the way, have you read any interesting books lately?
Used after the plain past form of a verb (〜たところで) to mean 'even if (something happens), (it won't change the result)'.
今行ったところで間に合わないよ。
Even if you go now, you won't make it in time.
説明したところで彼の考えは変わらないだろう。
Even if I explained it, his opinion probably won't change.
何回注意したところで、同じミスを繰り返す。
No matter how many times I warn him, he repeats the same mistake.