The Two Phases of Ejaculation

Emission is when the sperm is prepared for release from the body, just before expulsion.  It is mixed with several substances including fluids from the seminal vesicles and prostate, to form semen, ready for use.

Ejaculation Proper is when the semen is released from the penis in spurts, occurring once enough semen is produced to be ejaculated through the urethra.  Once this process has started, it is impossible to stop.