The Lense Flare plug-ins, which are part of the PixelFX plug-ins set, simulate the effect of streaks and spots of light caused in real cameras when light enters and bounces inside a camera lens. This plug-in set contains geometries that simulate different shapes, which can be used for lens flare or simple flare effects.
The Flare draws itself as a combination of geometry shader and pixel shader.
When a Flare Container is created (1) a non-editable pixel shader (2) is automatically added to the created Flair Container.
The non editable shaders are needed to do more (detailed, on a per pixel basis) graphical effects on the GPU (manipulating colors, textures, lighting, etc.), which cannot be done with Geometries only.
Note: This plug-in is located in: Built Ins -> Shader -> PixelFX