How does ParticlePointMesh works

I can not find any Index buffer. I believed that opengl couldn’t work without triangles. Obviously I’m wrong.

What should I read to understand clear mechanics behind ParticlePointMesh?

OpenGL supports points, lines, triangles, quads, and polygons. So it can work without triangles.

OpenGL can also draw meshes without an index buffer, then each set of primitives in the vertex buffer is drawn in order.

There’s some info here about them: