Well by the family there is no true difference between egret and herons, Truth is egrets are Herons.
The classification of the individual heron and egret do not form a biologically distinct group, they are same and even for bitterns.
Egrets are long-legged wading birds with mostly white or buff plumage and milky white during the breeding season.
Types of Egret found in India are Little egret, Cattle egret, Intermediate egret and Great egret.
Herons are also freshwater and long-legged birds from the family Ardeidae.
The herons are medium to large-sized birds and decorative plumes in breeding plumage like Purple heron and Grey heron.
Bitterns are also bird of the the heron family Ardeidae and more secretive than other members of the family. There are five types of Bittern found in India, listed below.
Cranes, Storks and Heron are long legged freshwater and coastal birds but differ in flying and their necks