Avina is the Citadel VI, first encountered by Commander Shepard near the Embassies on the Presidium. Like all VIs it appears as a hologram: Avina takes the form of an asari. It has several terminals around the Presidium, often near points of interest such as the Relay Monument or the Krogan Monument, and can answer any questions Shepard might have, giving guidance and a brief insight into galactic events.
Being a VI, Avina's capacity for discourse is limited; if Shepard asks for Avina's opinion on a subject, or if the Commander's questions get too politically charged, Avina says it hasn't been programmed with the parameters to answer. If Shepard tells Avina about being invited to the Council Chambers, it says that is a rare privilege; it states that it would be jealous, but that is beyond the scope of its programming.