Give birth to unreacted particles eventually

Support Particles and Physics Simulations
1

Hi,
I’m trying to ensure the correctness of Vietnamese translation of RNA texts and I came across this group of text in (source/blender/makesrna/intern/rna_particle.c) :

/* flag */
prop = RNA_def_property(srna, “use_react_start_end”, PROP_BOOLEAN, PROP_NONE);
RNA_def_property_boolean_sdna(prop, NULL, “flag”, PART_REACT_STA_END);
RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
RNA_def_property_ui_text(prop, “Start/End”, “Give birth to unreacted particles eventually”);
RNA_def_property_update(prop, 0, “rna_Particle_reset”);

Could anybody who understood what the feature (start/end) here is doing, and how to make a good example of the feature, please help me explaining it? I have no clue what it’s supposed to do.

Thanks in advance.