A Missional Community is a group of between 20 and 50+ people aimed at either a geographic location (a neighborhood) or an existing network of relationships. Missional Communities are often described as “small enough to care but large enough to dare.”
Key to the success of Missional Communities is the participants finding their primary identity of “church” within this community, rather than, say, a larger Worship Service on the one hand or a Small Group on the other. In essence, this group of people becomes a close-knit spiritual family on mission together.
The group balances its energies between an upward movement towards God, an inward movement toward the Missional Community as a place of identity, and an outward movement to represent Christ to their mission context. When they gather, they express this in creative ways that are appropriate to their context. In fact, there will be great diversity between groups in how this looks, with a variety of faces and voices being given room to step forward and contribute what they can. The only ‘rule’ is that they do not try to do a miniature version of a Sunday church service. [Alex Absalom - Launching Missional Communities]
Missional Communities often have Small Groups [M-Pods] which work as places of support, challenge and closeness, as the wider MC gathering can be too large for general sharing of prayer requests and the like. MC's also gather once a month with the larger church body for a Celebration Service. This usually involves a time for corporate worship, teaching, stories and re-envisioning the wider community.
Here's a slightly cheesy (but fun) commercial which gets the idea of extended family across . . .