ParticleSystem contains of dynamic particles, which spawn at emitters and die after a given time. The way they move and appear is controlled by the particlescript, which has its own detailed manual. All particles of a system are rendered at the end of a l3dset and a particlesystem can be used in only one l3dst. If you want to use the same particlesystem in multiple l3dsets, use one forceload per l3dset.
Compared to ParticleClouds you cannot control particles individually.
o-+ resource o-+ particlesys