What is Go (quiescent phase) of cell cycle?

What is Go (quiescent phase) of cell cycle ?

What is Go phase ? What is significance of it ?

There are two types of cells in adult animals :
(a)The cells which do not appear to exhibit division e.g., heart cells.
(b)Many other cells divide occasionally as needed to replace cells that have been lost because of injury or death of cell.
┬ęThese cells do not divide further and enter in an inactive stage called quiescent stage (Go) of cell cycle.
In this stage cells remian metabolically active.