WHAT IS SLi? and what is worthy nearly it?

WHAT IS SLi? and what is worthy nearly it?

Scalable Link Interface (SLI) is a method developed by NVIDIA for linking two (or more) video cards together to produce a single output. SLI is an application of parallel processing for computer graphics, expected to increase the processing power available for graphics. With SLI, it is possible to roughly double the amount of graphic complexity that can be handle by a computer just by adding up a second identical video card.