Getting a CFG form the CFL

Question

Can Any One explain this Language how we converted to CFG

Give a CFG for the CFL: {ai bj ck | i ≠ j or j ≠ k }   //ai mean a^i

I have the answer but I need an explaination (Step By Step)

The answer :

S   -->   S1|S2
S1  -->   A Eab|Eab B|S1 c
A   -->   a|aA B--> b|bB
Eab -->   Q|a Eab b
S2  -->   Eac C|A Eac
C   -->   c|cC
Eac -->   Q|B|a Eac c