Used to refer to two or more people doing something toward one another; means "each other" or "one another." Common in polite speech.
私たちはお互いに助け合って仕事をしている。
We help each other and work together.
お互いの意見をよく聞いてから決めましょう。
Let's listen carefully to each other's opinions before deciding.
彼とはお互いに連絡先を交換している。
He and I have exchanged contact details with each other.
お互い様だから、助け合おう。
We're in the same situation, so let's help each other.