As say it's name, emit particles from a geometry. For further informations about particles systems, go check this part of the doc : ParticlesSimulate a particle systemRead More
This modifier can be added over an existing particle system to make some trails. But this can also be done with EmitEmit a number of particles from another particleRead More. Go check the Particle RuleDefines the behaviour of particlesRead More part of the doc.
Beware that number of emitted particles represent the total of emitted particles. If you put this modifiers with a rate of 30 particles/seconds over o system containing millions of particles, you'll get 30 particles/second as a result.
Check this quick tutorial to see a little bit an extensive use of this modifier. This tutorial was made on an earlier version of Smode so the "place" modifier you see in use is the actual 3D TransformChange every vertex position using scale, rotate and translate transformationsRead More