With the Particle System Node you can insert a particle emitter into the scene. A Particle System node can be one of these types: Point, Box, Sphere, Animated Mesh Node, Cylinder, Mesh, Ring. These types describe the shape of the emitter.

What is actually emitted is similar to a Billboard node object.

A Particle System Node also can one or more Effectors. An Affecter is something located at a X,Y,Z position within the scene and will affect particles generated by the node object in different ways. The different types of Effectors are ‘Attraction’, ‘Fade-Out’, ‘Gravity’, ‘Rotation’, ‘Scale’.