This letter was written to the church in the city of Ephesus (in modern-day Turkey), possibly while Paul was under house arrest as a prisoner in Rome. The letter to the Ephesians covers many practical issues for Christians and the church, including how to live and work together, being united and recognising God's work through Jesus.
Ephesians gives us a great overview of what God has done through Jesus and what that might mean for the way we live. The people in the church in Ephesus lived in a culture that was pretty messed up, so the letter was teaching them how to live in the midst of this broken word. Even if the brokenness they saw was different to the brokenness we see, Ephesians is packed with good stuff for us to read.