Groundshare is the principle of sharing a stadium between two local sport teams. This is usually done for the purpose of reducing the costs of either construction of two separate facilities and related maintenance.
This is 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 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, such as the New York Giants and New York Jets sharing MetLife Stadium.