The stability of an object is related to the position of its center of gravity (CG). If the vertical through the CG passes through the base of an object, then it is stable, otherwise, it is unstable and topples down. Bodies with low CGs and wide bases are more stable.
Examples showing the relationship between the stability and center of gravity of a body
Here are some examples showing how the stability of a body depends on the position of its center of gravity (CG).
Related study: CG definition & location of CG in some regular objects