can anyone just explain What is the usage of Specular, Ambient, and Diffuse properties of light.. if u can please give some examples..

Diffuse - specifies how much/how model will be lit when the model receives light. (how much light should it reflect and absorb)

Ambient - specifies how much/how model will be lit when the model does not receive light. (Indirect light, the model would be lit by a uniform colour all over.)

Specular - when light strikes a smooth surface, they generally reflect in a sharp direction. This forms a specular highlight and it is viewport dependent. I think it is harder for me to explain you this because i suck at explanation. I think you should refer to a book, I'd suggest Frank D. Luna's DX11 book.