You will understand what the church of Ephesus looked like in the first century. Paul, Timothy, John and the mother of Jesus, Mary were all there. It was a famous church that had sound doctrine. But Jesus has to correct them and tell them to go back to their first love and the things they did at first. 

Not only does this letter to this church apply to way back then, but it applies to the churches today. It also applies to you personally. 

But there is more, this church also represents the first of the seven golden lampstands, in-other-words, it represents the early church in church history.