Uniquely, the asari are known to be perceived as attractive to many other species.
Asari resemble humans in terms of basic skeletal structure with five fingers on each hand and foot that are relatively straight (certainly in comparison to species like quarians and turians). A typical asari has a blue to purple complexion, though a teal complexion is possible albeit seemingly rare.
Asari are a mono-gendered species with no concept of gender differences.
According to Liara, "male and female have no real meaning for us," and, if asked, says that she is "not precisely a woman." At the same time, asari are often viewed as an all-female race, including by the Codex and by the Galactic Codex: Essentials Edition 2183.
Instead, the asari uses the meld to explore her partner's genetic heritage and pass desirable traits on to any offspring and as a "map" to randomize the genes of the offspring.
Additionally, pairings with krogan are not affected by the Genophage.
Liara melds with Commander Shepard several times for the purpose of viewing and helping understand the visions Shepard received from the Prothean beacon.