Takes a node of type Value and is the setting for an emission rate.
Although this node is optional (and is of no use for a Particle Grid Emitter), you need it in a Particle Mesh Emitter to define the exact amount of particles.

Takes a node of type Alignment. It is used currently only when emitting Vorticity particles to initialise their vorticity direction when they are born.

Takes a duration node that defines how long the node operates that is using these emission settings. This node is optional.

The FPS the emission should use (is useful if you use a different render FPS).

Shot will enforce that the emitter using these settings will emit the particles directly and not time integrated (not based on the current sub time step).
So deactivated the particle count is emitted per second and if activated per frame.

Only available if a duration node is linked. Allows to define the particle count strength in the range of the duration sequence.

Jitters the particles randomly to make their distribution more irregular (this can be beneficial in a liquid simulation).
100% means full jiterring intensity, 0% means the particles are placed ordered (in a regular fashion).