You would think that evangelicals would have no trouble answering this question. But ask 10 born again believers and expect as many different answers. So what is ‘evangelism? As a starting point, a study of the word evangelism (the noun) and to evangelise (the verb) is critical. Paul the Apostle borrows the noun ‘evangel’ from secular Greek. It means ‘to announce the good news’. Typically a runner (the carrier of the good news – the evangel) would enter the presence of the king or ruler and announce a military victory – the good news. The announcement of the good news was an event. The word ‘evangelism’ also has roots in the LXX (the Greek Old Testament). Isaiah, for example, is the herald who announces the good news of God’s salvation to Israel (e.g. Isaiah 52:7) The announcement is a specific event. But what are we to announce? The good news of the Gospel of Jesus Christ.
JI Packer says …
“What is evangelism? It might be expected that evangelical Christians would not need to spend time discussing this question. It would be natural to assume that we were all perfectly unanimous as to what evangelism is. Yet in fact, much of the confusion in present day debates about evangelism arises from lack of agreement at this point. The root of this confusion can be stated in a sentence. It is our widespread and persistent habit of defining evangelism in terms, not of a message delivered, but of an effect produced in our hearers.” 
“Evangelism is a work of communication in which Christians make themselves mouth pieces of God’s message of mercy to sinners. Anyone who faithfully delivers that message, in a small meeting, from a pulpit, or in a private conversation, is evangelising. The way to tell whether you are in fact evangelising is not to ask whether conversions are known to have resulted from your witness. It is to ask whether you are faithfully making known the gospel message.” 
What Packer is saying is very simple. Firstly, when a non-church person has heard the gospel, they have been evangelised. If a non-church person has not heard the gospel, they have not been evangelised. Second, the gospel is a specific message, intended to be spoken. Thirdly, evangelism is not to be equated with ‘results’. In other words, if a person hears the gospel and they do not convert, they have still been evangelised because they have heard the gospel.
John Stott concurs with Packer on these points…
“Evangelism is neither to convert people, nor to win them, nor to bring them to Christ, though this is indeed the first goal of evangelism. Evangelism is to preach the gospel” 
Understanding the original Greek and Old Testament roots of this word evangelism, and paying careful attention to scholars like Packer and Stott is critical, because together they clarify what evangelism is not. Evangelism is not saving people, this is God’s job (hense the title of “Saviour”). When we understand what is our job and what is God’s job, this lifts a huge burden off our shoulders and helps us do what we are called to do, and leave the saving up to God. And therefore the Glory goes to God!!!
John 6:65 “No one comes to the Son unless they are drawn by the Father”
Packer and Stott are not alone in defining evangelism in this way, there is actually remarkable agreement among the scholars on this, along with the agreement of thousands of key Christian leaders which you see in documents from worldwide conferences on evangelism, e.g. the Lausanne conference  and ‘This we Believe’ .
You will also note that Evangelism is not a process as many have suggested. Rather, evangelism is a very specific event (the proclamation of the gospel) within the process of someone coming to Christ. The big question from here is, what is this Gospel that we are commanded to preach?
Does the definition of evangelism really matter?
Yes. Many in the church define any type of outreach or connection with non-church people as ‘evangelism’ and therefore believe that they are evangelising, even without the proclamation of the Gospel. This is a deception and can lead to Christians feeling like they have ‘done their part’, even when the Gospel has not been proclaimed.
 J I Packer. Evangelism and the Sovereignty of God. IVP. 1961. p37 Google+
 Ibid, p41
 John R.W Stott. Christian Mission in the Modern World ( Downers Grove: Illinois, Inter Varsity Press, 1975), 39
 See The Lausanne Covenant, from “Let the earth hear his voice”. (World Wide Publications), 1974, p25.
 See Ravi Zacharias et el. This We Believe. The Good News of Jesus Christ for the World. Zondervan Publishing House. 2000. p 248