TV Line, or Television line (TVL), is used in analog camera, and is a specification of an analog camera’s or monitor’s horizontal resolution power. It is alternatively known as Lines of Horizontal Resolution (LoHR), aka lines of resolution.
The TVL is one of the most important resolution measures in a video system. To put it to a simple explanation, the more the TV Lines (depending on the size of lens), the better picture quality.
For the analog cameras, for normal commercialized home and office use, currently, 1200TVL is the maximum TV Lines you can find on the market. Anything above that is only used for special purpose.