Little more than slower, armed shuttles, corvettes (formerly known as "rookie ships" or "noobships") are the basic frigates that new pilots start with. You can acquire a new corvette (together with a civilian weapon, a civilian mining laser and one unit of Tritanium) for free by clicking on the "Board my Corvette" button while docked in a station. On their own these are not much use for anything other than basic errand-running.
All four corvettes can carry at least one light drone in their dronebay. The Gallente Velator can carry two.