Function, Constructor, Operater overloading comes under 
compile time polymorphism and function overriding, virtual 
functions come under runtime polymorphism.

polymorpism is of two types 
1)compile time polymorpism 2)run time polymorpism

compile time polymorpism:-it can call the functions during
compile time example:-opporator overloading 
in the operater overloading based on the parameters and
return type of the functions are called

runtime polymorpism:-it can call functions during runtime 
example:-opporator overridding
in opperator overridding the functions in both base class
and derived class have same signature(same parameters type
and same return type) based on the object used appropriate
method will be called