the.com/birds and the bees

means A euphemistic way of explaining human reproduction and sex to children by dressing it up in nature imagery instead of plain anatomy.

from The phrase draws on a long poetic tradition of using natural pollination and courtship — bees gathering pollen, birds pairing off and nesting — as a genteel stand-in for sex and procreation, letting embarrassed adults gesture at biology without naming it directly. The exact coinage is hard to pin down, though the idiom as we use it today solidified in English by the early 20th century, likely nudged along by poets and euphemism-hungry parents alike. The popular notion that it comes from one specific poem or source is mostly folklore; really it's a gradual cultural shorthand, not a single invention.