what is meant by polar and non-polar nature of an element?

Dear student term polarity is used for a molecule or a substance or for an covalent bond.It describes the tendency of a substance to have a molecular dipole,or a positively and a negatively charged end.Polar molecules are those molecules which are made of elements with different electronegativities,meaning that one element possesses the shared electrons more often than the other due to which the more electronegative element gets partially negative charge and the more electropositive element gets partially positive charge.
For ex- if we consider a bond between two atoms,A and B and both atoms are equally electronegative,both have the same tendency to attract the bonding pair of electrons,and so it will be found on average half way between the two atoms.For example, H2 or Cl2 molecules.
But in case when B is more electronegative than A,it will attract the electron pair rather more than A does.Due to this the B end of the bond has more than its fair share of electron density and so becomes slightly negative and the A end (rather short of electrons) becomes slightly positive.For ex- HCl,H2O molecules.

Covalent bond can be formed between two similar atoms as well as disimilar atoms.If such bond is formed between two similar atoms,then shared pair of electrons lie midway between the nuclei of two atoms because both the atoms have the same attraction for the bonding electrons.Such a covalent bond is called as non-polar covalent bond and the molecules will be called as non-planar molecules.For ex- formation of H₂,Cl₂,O₂,N₂.
But in case the colvalent bond is formed between two dissimilar atoms,then bonding pair will displaced towards the atom which has more value of electronegativity.This electronegativity is the power or ability of an atom to attract the shared pair of electrons towards itself in a molecule.
Since the shared electron gets unequally distributed due to electronegativity difference,there will be a partial negative charged develops on more electronegative atom indicated as^--,while a partial positive charge indicated as ⁺ develpos on less electronegative atom.Such a covalent bond is called as polar covalent bond and the molecules are reffered to as polar molecules.For ex- HCl the shared e- pair is displaced toward Cl because of more electronegativity than H so the bond will be polar and the molecue is polar in nature.