In some parishes, they only celebrate the Divine Liturgy once on Sunday and once on a weekday. The rest of the time they have Orthros in the morning.
And yes, it is the prayer of the Church (corporate prayers) or common prayers.
Great Vespers is served before a feast day or on Saturday Evenings. In some parishes this Great Vespers is called All-Night vigil because it includes Vespers, Compline and Orthros. So, Vespers on Wednesdays will only become Great Vespers when there is a major feast day falling on Thursday, like the Annunciation or some other feast day.
Hope this helps.