Enantiomers are molecules that have  opposite spatial configuration are said to be optically active.

One enantiomer will rotate polarized light a set number of degrees to the right. This is called the dextrorotatory isomer or (+) isomer.

The other enantiomer will rotate the plane polarized light the same number of set degrees in the opposite left direction. This isomer is said to be a levorotatory isomer or (-) isomer.