The DC Metro Area is the name given to the metropolitan area that is DC, Northern Virginia (commonly called by the locals as NOVA), and the Prince George, Montgomery, and sometimes Howard and/or Fredrick counties of Maryland. It sometimes includes Jefferson County, West Virginia due to many commuters living in the area. More commonly, it applies to the area that is connected by bus and train (locally known as Metro). The DC metro area is connected together by the WMATA through its flagship "Metro" bus and rail brand. It is also aided by smaller bus routes in Maryland and Northern Virginia (Fairfax Connector), ART (Arlington Transit), REX, PRTC etc).
I live in the DC Metro Area. Having a car is not a must here but it is more convinient. You can get to major parts of the DC metro area through the Metro Bus, Color coded Metro Rail. Fairfax Connector, Arlington Transit (ART), Richmond Highway Express (REX), Prince William Transit (PRTC/OmniBus), and other small bus routes. The only inconvenience is that you have to live in a lenient urban area to be serviced. It is rare to see a bus in the suburbs (such as Fairfax Station) than it is near major well known cities (Springfield, Alexiandria - Which is divided into Mt. Vernon, Hybla Valley, Franconia, Kingstowne, Belle Haven, Ft. Hunt and Huntington)