Like rigid body objects, particles are moved dynamically using collisions and fields. In short, a particle is a point in space that is given renderable properties—that is, it can render out. When particles are used en masse, they can create effects such as smoke, a swarm of insects, fireworks, and so on. nParticles are an implementation of particles through the Maya Nucleus solver, which provides better and easier simulations than traditional Maya particles.
Although particles (and nParticles) can be an advanced and involved aspect of Maya, it’s important to have some exposure to them as you begin to learn Maya.
Much of what you learned about rigid body dynamics transfers to particles. However, it’s important to think of particle animation as manipulating a larger system rather than as controlling every single particle in the simulation. You control fields and dynamic attributes to govern the motion of the system as a whole.
For example, with the pool table, you control the motion of the cue ball and let Maya dynamics calculate the motion of the other balls after they collide. Each ball is a distinct part of the scene and renders out as a distinct object in the frame. Particles are most often used together in large numbers so that the entirety is rendered out to create an effect. To control a particle system, you create an emitter and define fields and attributes that control the particles’ movement.