Ejaculation can also occur during sleep, known as a nocturnal emission or wet dream, where the male has no control over the spontaneous ejection of sperm from his unstimulated penis.
A usual precursor to ejaculation is for a male to have an erection, which then allows the penis to be stimulated.
When a man has undergone a sufficient amount of stimulation on his erection, ejaculation begins. Sperm is pumped out of the penis with rhythmic contractions, each contraction spurting more and more sperm out. A typical ejaculation consists of 10-15 contractions.
In order to get to this process, a man must stimulate genitals in some way (whether that be through fellatio, sexual intercourse or just masturbation) with an erection, in order for the fluids from the testicles to build up towards the penis.
Other than that, it is pretty self-explanatory.
Stan: Oh, I just watched some porn and ejaculation occurred.
(n):“e-jaculation is the e-ville epidemic of our age”