What is difference in malic acid and dl malic acid?

There are two different structures of malic acid, an L-isomer and a D-isomer. The only difference between the two is that they rotate the light shining on them in two different directions.

L-Malic acid is produced naturally in fruits. 90% of the acid in Apples is malic acid.

When malic acid is produced synthetically, a mixture of the two isomers is obtained which is called DL-malic acid (because it contains both D- and L-malic acid).

When you eat DL-malic acid, your body digests it in just the same way as it does for L-malic acid. It is part of the Krebs cycle.