Author - Paul (although like everything some dispute it) who likely wrote it while imprisoned in Rome. Paul was a founder of the church in Ephesus, and if you read the book of Acts you can tell that he had great love for the Ephesian believers and the elders.
Audience - the church at Ephesus. Back in the day churches met in homes, so this letter probably circulated among the house churches in Ephesus and eventually to other churches as well. The church at Ephesus consisted of Jewish and Gentile believers worshipping together. Here are some facts about Ephesus:
- Busy commercial port with a steady flow of cosmopolitan people
- Worship of the fertility goddess Diana was a important part of the city's commerce. The temple was an ancient wonder of the world, and you may recall the anger of the silversmiths when Paul began converting people away from worship of Diana.
- People could participate in any sexual lifestyle or they chose without any cultural opposition.
Purpose - In a nutshell the first part of Ephesians focuses on Christians doctrine and our riches in Christ. The second section focuses on how Christians should live on a daily basis if they are truly allowing God to transform them into the image of Christ Jesus. It's a great book that has come up a lot lately for me in different situations, and I know it will bless you to read it!