What are we here for, and what is the church here for and how do we achieve it?
The word “church”, or ekklesia, just means a gathering of some sort. In early usage it is specifically Christian because they used that adjective in front of it! So that doesn’t help us much.
When Jesus called his first disciples, he told them what he wanted them to do as his disciples:
 As Jesus walked beside the Sea of Galilee, he saw Simon and his brother Andrew casting a net into the lake, for they were fishermen.  “Come, follow me,” Jesus said, “and I will send you out to fish for people.”  At once they left their nets and followed him. When he had gone a little farther, he saw James son of Zebedee and his brother John in a boat, preparing their nets.  Without delay he called them, and they left their father Zebedee in the boat with the hired men and followed him.
So, what was Jesus ultimate purpose in calling his disciples? So that they would fish for people – so they would play their part in making other disciples.
What was Jesus’ method in doing this?
When told that lots of people were seeking him because he was healing people…
 Jesus replied, “Let us go somewhere else—to the nearby villages—so I can preach there also. That is why I have come.”
Jesus’ method was to preach to the people. The healing was purely an aid in achieving that aim.
When he preached, what was his message?
Mark 1:15 (and Matthew 4:17)
“The time has come,” he said. “The kingdom of God has come near. Repent and believe the good news!”
So, the people were repent – to turn from their sinful ways, and turn back to God, because God’s kingdom was coming near. In fact that was the same message that John the Baptist had been proclaiming earlier in preparation for Jesus’ ministry. Repent.
Jesus said he came to preach, but that was only one of his aims, his initial aim. We are told of his ultimate aim by Paul:
1 Timothy 1:15a
 Here is a trustworthy saying that deserves full acceptance: Christ Jesus came into the world to save sinners
He achieved that by dying on the cross and rising again 3 days later.
After Jesus rose from the dead, before he was taken up into heaven, he gave his disciples their orders as to what they were to do after he was gone:
In John 20:21
 Again Jesus said, “Peace be with you! As the Father has sent me, I am sending you.”  And with that he breathed on them and said, “Receive the Holy Spirit.
Jesus was sending them out into the world to do what Jesus had been doing. He said he would give them the Holy Spirit to equip and empower them for the task.
Matthew tells us of another time Jesus told his disciples what they were to do:
 Then Jesus came to them and said, “All authority in heaven and on earth has been given to me.  Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit,  and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age.”
So, again we have this emphasis of his people being sent out into the world to make disciples, and the way that is to be done is by teaching them to obey everything that Jesus had taught the Apostles.
Is this what they did? We see in Acts what the message of the early church was when they met non Christians:
 Peter replied, “Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit.  The promise is for you and your children and for all who are far off—for all whom the Lord our God will call.”  With many other words he warned them; and he pleaded with them, “Save yourselves from this corrupt generation.”
Sounds very much like the message of Jesus!
That was their message, but what did the Apostles do when they gathered together with other believers? How did they work this out in practice when they churched?
 They devoted themselves to the apostles’ teaching and to fellowship, to the breaking of bread and to prayer.
Again we see this emphasis of teaching. Added to that the group broke bread together – that may well have included communion, but probably just means they ate together – an expression of the fellowship they were devoted to, and they prayed.
Did the Apostle have the same message? Paul tells us of his emphasis as he sought to plant churches around the Mediterranean Sea:
1 Corinthians 2:1-2
[2:1] …When I came to you, I did not come with eloquence or human wisdom as I proclaimed to you the testimony about God.  For I resolved to know nothing while I was with you except Jesus Christ and him crucified.
I presume that meant an emphasis on Jesus and his death and it’s meaning and significance and outworking. That is the content of his letters and the sermons that Luke recorded in Acts. Basically the gospel message – the good news about the kingdom, that salvation is available to those who repent and believe the good news and how to live in the light of that.
So what should we be doing as a church?
Making disciples. Doing that by teaching people about Jesus and what he has achieved for us on the Cross and how that works out in our lives.
What was the result when they did that in the early church?
Those who accepted his [Peter’s] message were baptized, and about three thousand were added to their number that day.
In other words, disciples were being made and Jesus was building his church. And we should expect God to be at work in his harvest field today if we are faithful in fulfilling the task entrusted to us. In some places there may be 1000s added, in others, 1s, but he will build his church.
So, the question then for us is, for everything that we do, is it leading to that aim? Does it make disciples?
C. S. Lewis concluded:
[T]he Church exists for nothing else but to draw men into Christ, to make them little Christs. If they are not doing that, all the cathedrals, clergy, missions, sermons, even the Bible itself, are simply a waste of time. God became Man for no other purpose. It is even doubtful, you know, whether the whole universe was created for any other purpose.
C. S. Lewis, Mere Christianity (New York, Simon & Schuster Touchstone, 1996), p. 171. Quoted at: http://www.cslewisinstitute.org/The_Purpose_of_the_Church