the.com/facts of life

means The basic, often uncomfortable truths about how sex, death, or the world really work, which someone eventually has to explain to you.

from The phrase crystallized in the 20th century mainly as a euphemism for explaining human reproduction to children — 'the facts of life' standing in for sex because the plain word felt too blunt for polite parents. 'Fact' itself traces back to Latin factum, 'a thing done,' from facere, 'to make or do.' Over time the phrase widened beyond sex ed to cover any hard truth reality forces on you — death, money, disappointment — the lessons life hands out without a syllabus.