1 SO2 and SO3
Both of them are the common oxides of sulfur, in which SO2 implies sulfur dioxide, and SO3 stands for sulfur trioxide.
2 What is the difference between these two compounds?
SO2 and SO3 are oxides of sulfur that are formed from the reaction between sulfur and oxygen molecules. SO2 is comprised of 2 oxygen atoms bonded to a sulfur atom, whereas SO3 has three oxygen atoms bonded to a sulfur atom.
3 Formation of Sulfuric acid
Sulfuric acid is formed with the reaction of oxygen and sulfur dioxide in the presence of catalysts, SO3 fumes robustly as soon as it gets in contact with moist air and dissolves in water. The whole process tends to generate intense heat, causing it to form sulfuric acid. (See What Does A Barometer Measure?)
4 Is it true: SO2 is polar, and SO3 is non-polar?
The statement is evidently true. The sulphur-oxygen bonds are distinctly polar are indeed polar due to electronegativity difference between SO2 and SO3. SO2 molecule is identical to H2O as it has a bent shape with C2v chemistry. Vector of the two S - O moments is due to the net dipole moment, which makes the SO3 molecule non-polar.