to be helpful; to be useful (to serve a purpose or provide benefit).
このアプリは旅行にとても役に立つ。
This app is very useful for travel.
彼のアドバイスが試験勉強に役に立った。
His advice was helpful for studying for the exam.
簡単な英会話フレーズは海外で役に立つ。
Simple English conversation phrases are useful abroad.