tl;dr: Catholic canon says that the cracker and wine literally become the actual flesh and blood of Jesus when they are "consecrated" (whatever the hell that means).
It's even more bonkers that if you puke after communion, it un-tra substantiates and turns back into normal bread and wine. This is why we can never observe the magic.
Every time i think of this song I'm reminded how funny it was to me to hear the radio edited version of this song which removed all references to suicide which if you recall the song was most of it.