Can any one explain me the structural difference between Proteins and Peptides?
In terms of structure: both are composed of amino acids. 

A peptide is when at least two amino acid are linked together.
A protein is composed of multiple amino acids and have a secondary, tertiary and even quaternary structure.

In terms of function: larger molecules have more complex functions.

Peptides can act as a intracellular or extracellular ligands which will activate a signal.

Proteins have a large array of functions (enzymatic, structural, receptors etc)

This article explains in more details the differences in proteins structure and functions:https://en.wikibooks.org/wiki/Structural_Biochemistry/Proteins