You can find the Illustrator polar grid tool beneath the line segment tool in the tool box
Double click the tool's icon to display all the settings. Next time you create the design, these will be the settings used though the height and width are overruled by the actual dragging of the mouse to create the grid. The key settings are the concentric and radial but you can also introduce some skew into the settings (though I wish randomization was also available)
Set the concentric to generate rings / circles. The tool create standard paths with fills and strokes, it is not a live object (as yet but many of the tools are now live). You can set the value from 0 to 999 (max)
Sets the number of spokes. You can use this to create intense starburst designs. You can set the value to 0 as well as increase it to 999 which is the max. One annoying thing is that the outer circle still has to be removed and is not part of the count, to do this, use the ungroup.
You can set the skew to be positive or negative and for both settings. Personally, I rarely use them and would prefer a more random feature or perhaps different spacing methods used.
You don't have to use the tool only once. It can be used multiple times to fill the design. The design can also be quickly filled using the live paint bucket tool and clicking the individual cells and changing the colors of the live paint bucket using the left and right arrow keys. You can then fill the artwork with all kinds of colors to create the most amazing artwork and also you can still re-color it further if you expand the design (live paint needs to be expanded) and use the edit menu adjust color balance etc or use a third party plugin such as Randomino or Phantasm
It can be used with a standard fill and stroke but you can modify the stroke with width profiles to create far more dramatic artworks. Select the paths and then go to the width profiles at the top of the application. Select one of the width profiles or just go to the width tool and use that to modify the weight of the strokes at certain points
Select the path and go to the appearance panel found via the window menu. Go to the right side menu for the panel and select add new stroke. Goto the effects menu and distort and transform and then transform command enter a value in the horizontal and / or vertical move fields. You will now see two designs. You can then change the color of the second design via the appearance panel. Multiple artworks can be added this way. Other effects can be added as well as widths and dash
Select the path and then go to the effect menu and apply zigzag / blurs etc found in the distort and transform. The effect can be added to any additional strokes added via the appearance as well as the source path.