What are the different bases in DNA and RNA?

DNA and RNA have four different possible bases. 

DNA has C, G, T and A.
RNA has C, G, A and U.

So instead of the T in DNA, RNA contains U. 

What do the bases each stand for? 

C - Cytosine. 
G - Guanine. 
A - Adenine. 
T - Thymine. 

They pair by complementary base pairing.