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Well since you asked, your slightly off.
It's actually 640x480(out of 525 lines).
The horizontal lines for NTSC is actually 525 lines,
of which 480 contain picture information.
The best way to explain it is this way:
The size of a video image is measured in pixels for digital video or horizontal scan lines for analog video. Standard-definition television (SDTV) is specified as 640×480i60 for NTSC and 720×576i50 for PAL or SÉCAM resolution. New high-definition televisions (HDTV) are capable of resolutions up to 1920×1080p60, i.e. 1920 pixels per scan line by 1080 scan lines, progressive, at 60 frames per second.
There can be some additional confusion in the horizontal-resolution specification. When refering to fixed-pixel displays or the resolutions of digital-television formats, the term "pixel" is correct. When refering to an analog television's horizontal resolution, the term "TV Line" (TVL) is more appropriate. This specification is the number of vertical lines the television can resolve per picture height. If the set is driven by a signal of closely spaced alternating black and white vertical lines, we count the number of visually resolvable lines to determine the set's horizontal resolution.
Don't confuse these vertical lines with the horizontal scanning lines of a television. The number of horizontal lines is fixed at 480 in NTSC video, and can by 720 or 1080 in HDTV. (NTSC is actually 525 lines, of which 480 contain picture information. The other 45 lines are not displayed on the screen, and contain synchronization pulses, and information such as Closed Caption data.) The 480 lines you see are called active scan lines.
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