Volume

Takes a Volume to define the area in space where the emitter is allowed to emit particles.
Particle Goup

Link the Particle Group which should take the generated particles.
Particle Type

Defines the particle type to generate.
Passive
Vorticity
Liquid
Diffuse
Emission Settings

Link Particle Emission Settings in here that define the emission behavior.
Particle properties

The emitter will attach any particle property you assign here to each generated/emitted particle.
Remember that each particle automatically gets a Position and a Velocity property attached.
Exact evaluation

As the emission is based on a grid, the spatial emission check operates on each cell.
Particles are however emitted in a subgrid fashion and the check if the emitted particle is inside the given Volume happens in this subgrid
if Exact evaluation is activated. Otherwise it will only check once if the cell itself is in the volume (which is faster but not as exact).
Start Distance

Follows
End Distance

Follows
Particle Color

Follows
Distance to Surface [voxels]

Follows
Subdivisions > Distance

Follows
Subdivisions < Distance

Follows