Gospel Communities are people who take responsibility for each other as the family of God on the mission of God. 

They are not small groups — though there are small group elements. 
They are not Bible studies — though the Bible is studied. 
They are not accountability groups — though accountability does happen.

They are, in essence, "Bible obedience groups" where people help one another to walk in joyful submission to Jesus, in mutual loving submission to one another, and on the mission that He calls us to.