Minecraft wiki entry for Particles, associated text: The render radius of particles. It seems to be round, but not entirely circular, as seen at the back.
An annotated image of particles.png with the primary purposes of each particle texture explained.‌[Bedrock Edition only]
Old eating particles in Bedrock Edition, which appears as miniatures of the food itself.
A burning zombie in Bedrock Edition, emitting particles with fire's animation.