width: 0;\nheight: 0;\nborder-left: 50px solid transparent;\nborder-right: 50px solid transparent;\nborder-bottom: 100px solid #06b6d4;
It uses CSS borders. When width and height are 0, borders form 4 triangles. Setting colors and transparency shows only the desired direction.
Commonly used for tooltip arrows, dropdown indicators, and decorative UI elements.