In 3D modeling, edges are lines (straight or curved) connecting two vertices, forming the boundaries of a model’s faces (polygons).
Edges define a model’s shape—fewer make simple forms (e.g., a cube), while more add detail (e.g., a smooth sphere). They also let you edit: moving or adding edges changes how faces bend or fold.
For beginners, use edge loops (connected edges following a shape’s contour)—they refine features (like a character’s arm) without breaking the mesh.