As we process the Three Worlds (which we will do a lot), we begin with Michael Frost explaining what a missional church is and how it is differing from the traditional church. This is about a 55 minute talk, but it's well-worth listening to. It's inspiring and helpful in understanding the issues.
In general, these churches are making sure that they engage the secular and they are deeply concerned about making sure that people in their churches spend time in the world--as opposed to staying inside their church and trying to attract people.
We'll look at critiques against this later, but for now, this is a really good explanation of what the healthiest missional churches might look like.