Styli are tools for writing or drawing on a touchscreen device, like a phone or a tablet.
Styli are useful for drawing and writing on electronic things.
Examples:
I use a styli to draw on my tablet.
She bought a new styli for her phone.
The styli is very useful for drawing pictures.
I lost my styli and now I can't draw on my tablet!
With a magic styli, you can draw anything you want.
The styli is like a magic wand for drawing.