The A.C.T.S. model is based in Jesus' ministry and provides a framework for churches. Each stage highlights questions that individuals and churches need to answer if they are to be effective in mission. Answering those questions might revolutionise the church.
The basic idea is that, in Jesus' disciple-making ministry we see four phases that are cyclic:
Read A.C.T.S.: The Church's Mission In The Light Of Jesus' Mission for a much fuller exploration of this model.
...getting people's attention through revealing the Kingdom of God - miracles, healing, befriending, stories... Attracting drew crowds but crowds are generally interested in the spectacle and the personal benefits, not in the cost of following Jesus.
The ATTRACT phase is pre-evangelism
Jesus spelt out the cost primarily in terms of the gospel. Would people believe in, and follow, Him? Shallow crowds did not interest Jesus. He wanted to filter those crowds so as to find the few who were willing to go further. Often the crowds walked away when challenged. But some responded. The value of attracting crowds was that somewhere in those crowds were the few who would follow.
The CHALLENGE phase is evangelism
The few who responded needed to be trained. The obvious examples are the twelve disciples. Jesus invested huge time into them. His intent was to "make them fishers of people".
The TRAIN phase is discipling
When ready, Jesus commissioned them to repeat this process. We see that imitation of Jesus' method in the book of Acts.
The SEND phase is Mission
This video looks at the Attract (here called Invitation) and Challenge phases of Jesus' disciple-making.