Explain what d and l represent in stereoisomers

Stereoisomers are isomers that have the same connectivity between their atoms but differ in the arrangement of their atoms in space. Specifically, D and L stereoisomers allow to designate the dextrorotatory and levorotatory carbons respectively of the molecules with a single asymmetric carbon.

Explanation:

A dextrorotatory carbon rotates the polarized light in a clockwise turn and a levorotatory carbons rotates the polarized light in counterclockwise turn. Also, there is a designation Rule for L and D carbons. First, the molecule is represented in Fischer projections with the carbon chain in the vertical direction and with the most oxidized side up and the smallest down. Second, the groups that integrate it towards the back of the plane are represented backward. Finally, the D stereoisomer will be the one who presents the functional group to the right and the L stereoisomer will be the one who presents the functional group to the left.

The most common example of D and L stereoisomers is D-glucose and L-glucose, both differ on the orientation of the -OH group at the carbon 5.