Purines and pyrimidines are the two classes of nitrogenous bases in the nucleic acids (DNA and RNA).
Purines are nine membered, double-ring compounds whereas pyrimidines are six-membered, single-ring compounds.
There are two purines- Adenine and Guanine whereas there are three pyrimidines- Cytosine, Thymine and Uracil.
Adenine, Guanine and Cytosine are present in both DNA as well as RNA whereas Thymine is found only in DNA and Uracil only in RNA.
