This is where two teams that do not play the same sport share a ground or a stadium. It is common in North America to see the sports of baseball and football to be coupled (although this trend is being discontinued as costs of adapting multi-modes rise). Similarly, there is a coupling of basketball and ice hockey. Two teams from the same region which play the same sport will accommodate each other by sharing grounds.
This is where two teams that play the same sport share the same ground. These may be two non-competing teams who play at different levels, such as Bury F.C., renting Gigg Lane to F.C. United of Manchester in England.
This is where two teams in the same league share the same ground.