Choose whether the particles will be emitted in the shape of a cone or pyramid.
Give the size of the emitter. You can also scale the emitter by selecting the Scale tool and dragging in the viewport.
These parameters set the value of the emission angle.
If Emitter Type is set to Cone, the horizontal range is from 0° to 90°; with the Emitter Type set to Pyramid, the horizontal range is from 0° to 360° and the vertical range is from 0° to 180°.