Here the words "pour out" mean to give generously and abundantly. Alternate translation: "I will give my Spirit abundantly to all flesh" (See: [[rc://en/ta/man/jit/figs-idiom]])
This is a hyperbolic metonym that refers to all people by speaking of them as all living creatures, who have flesh. Alternate translation: "all people" (See: [[rc://en/ta/man/jit/figs-hyperbole]] and [[rc://en/ta/man/jit/figs-metonymy]])