As the name implies, this setting uses two different brush shapes to create the final sample. Key commands make repetitive actions quicker and easier.
Photoshop's Quick Mask mode doesn't just give us a different way to view selections. Then, I'll click on the Quick Mask icon at the very bottom of the Tools panel. Scattering The Scattering menu allows you to vary where each sample of the brush is placed and how many samples are placed per step.
It also requires a bit of talent mixed in with never-ending practice. To change the spacing, type a number or use the slider to specify a percentage of the brush diameter.
Spacing can also be turned off using the checkbox next to its name. Use key commands. Paint over corners, not into them.
All I can do is guess at a value. The photo layer is selected and active: The Layers panel showing the photo sitting above a white-filled background. The Direction control rotates your brush so that it naturally follows the curve of the stroke.