If a strain is described as balanced or 50/50 or (50:50, aka 1:1), then it implies that it is genetically a hybrid strain that is made from 50% sativa and 50% indica strains.

If the effect is called balanced, then it implies that the strain gives a balance between an indica and a sativa effect, that is, a body-high, relaxing, sleepy effect versus an energizing, thought-provoking effect.

A balanced effect would be neither too sleepy nor too stimulating.