Question

what is p pie p pie and d pie p pie bond?

Answer 1

pπ-pπ bond is formed when a p orbital of one atom bonds sideways with a p orbital of another atom.  Both orbitals have partially filled orbitals.  
Like   C = O,  C + N, C ≡ N,  C = C..

pπ-dπ bond is formed when a p (or a pˣ) orbital of a ligand , containing both electrons, reacts with an empty d orbital of a metal (transition). Nickel Carbonyl Ni (CO)4 is such an example. 

Answer 2

Explanation:

Sigma bond: A covalent bond resulting from the formation of a molecular orbital by the end-to-end overlap of atomic orbitals, denoted by the symbol σ.

Pi bond: A covalent bond resulting from the formation of a molecular orbital by side-to-side overlap of atomic orbitals along a plane perpendicular to a line connecting the nuclei of the atoms, denoted by the symbol π.

now, coming to the explanation part:

If there is bonding between two atoms where one atom is having one vacant orbital and another is having one lone pair of electrons, then this electron pair is donated to that respective vacant orbital ..then this bonding is called p-p or p-d depending upon the orbital to which the pair is donated and from which the electron pair is donated. if both the orbitals are d, then its called d(pi)-d(pi) bonding. these bonding are also called back-bonding bonds.

Eg.

in BF3, B has incomplete octet so a fully filled p(pi) orbital of F donates a lone pair of e to the vacant orbital of B. so here pp(pi)-p(pi) bonding occurs and is known as back-bonding also.