Damiana Leaf is a supplement consisting of the dried leaves of the Turnera Diffusa plant, which has traditionally been brewed as a tea for use as a physical tonic and aphrodisiac in Central America (with some references to the Mayan culture, but more recently Mexico).
Evidence on Damiana Leaf is lacklustre. Not too many studies have been conducted on it, and most are studies attempting to isolate bioactive ingredients from the compound. Two studies have been conducted in rats showing aphrodisiac properties when the rats are either sexually sluggish or fatigued, which is an effective that can possibly be mimicked by any adaptogen class supplement and more of a credit to the 'physical tonic' aspect of Damiana than the aphrodisiac properties.
There is some limited evidence that it may reduce anxiety, but due to Damiana being a fairly good source of Apigenin these effects can probably extend to any Apigenin-containing plant, of which there are several (not limited to chamomile tea and lemon balm).
Beyond that, there is not much quality evidence to support usage of Damiana as aphrodisiac. All human studies using Damiana are currently confounded with usage of multiple bioactive components which complicates assessment of Damiana itself.