Simply knowing the significant wave height and dominant wave period is great — if you are a boater!
But as a surfer, knowing each individual swell predicted to arrive at the beach is essential, not just what will be dominant. Two days with identical estimated surf height can look completely different, depending on the underlying individual swells. Take a look here for more information on swell vs surf.
Theoretically we can have an infinite number of swells in the water (depending on how far you want to break down the sea state) but usually we have about at least 2 and upwards of 3-4 swells in the water at any given point/time.
The Swell Analysis tool is designed to visualize individual swells detected by the model by laying them out over time. Each colored line (see below) represents an individually sorted swell in the water. The position of the line on the graph represents height; the size of the arrow represents period, and the direction of the arrow gives us the direction of each swell.
As you can see to the right of the graph's title, you really want to be looking out for Highlighted Conditions. A yellow bar means swell at that moment in time meets a predetermined threshold for ideal size/period/direction. Take a look here for more information about Highlighted Conditions.