Particles are very useful for complex animation where we have to animate large amount of objects like Rain, Dust storm etc.
In 3dsmax we have very strong particle system which is both event and non event driven.
The event driven particle are control by a various attribute which trigger animation, then this particle behave according to the event in which they are running. This type of particle system is known as Particle flow in 3dsMax. Non event driven particle system, particles show their typical behaviors throughout the animation, in 3dsMax they are snow, spray etc.

Particle Flow can be control by Particle view, where we create events and in events we have operators (operators define particle properties like rotation, speed, birth rate etc.). When we hit play button PF continually evaluates all events and operators step by step and update the particle system.

How PF works

PF base is particle view where you can edit your Particle Flow.
When you first create PF then in particle view you find a global event. Global event affect all particle in that system, you can add material to it so that each particle having same material in the system. Then after global event we normal or local event start, it usually start with Birth event (Which give birth to particles) then we have other operators which define speed, rotation, shape, display etc.
PF read all the operators in sequence in an event, for example if speed operator is come first against birth event then first speed calculated then it give birth to particle, therefore there is no use of speed and particle stay their only.
We can also apply different test to our particle system which check certain attribute and give dynamic property to particles.
For ex. We can check when our particles collide and also what if particle travel higher then given speed.

Particle’s Life

Yes particles also live their life as we do, they born, do some action and then die.

Birth operator give birth to particles according to the attribute you define, these attributes are when to start and stop creating particle and how many particle will be created.
Position Icon operator define from where new particle emit, here we can define that particle came out from one single point like water coming from tap, or they can also come out from surface like rain from cloud.
Particles remain on emitter, they won’t move at all because their in no force to make them move. Operators who moves particle are Speed and force operators, speed particle use inbuilt attributes to control the speed of particles like Speed, direction and divergence. Where as force operator use external forces (gravity, wind, motor etc.), here we pick force and that force will apply to PF.