Well if you want us to assume you're not being goady & are asking a "genuine" question, it comes from the latin, with peri meaning 'around'.
Whereas menopause is just one day in the entire lifetime of any woman (or maybe 2 if you're 'lucky' enough to experience a period again after 12+ months without).
As properly funded medical research is beginning to demystify more effectively over the last 20 years or so, "peri" menopause usually starts to kick in around 10 years before menopause day for most women.
And the relative ratios of hormones fluctuating so wildly over those 10+ years as well as falling levels compared to the regular menstrual years results in a whole laundry list of actual physiological differences occurring. Some of which can be wildly debilitating.
So 'peri'menopause more widely as a thing is simply a more medically accurate description of when most women will experience symptoms (10 years vs 1 day).
Delighted to hear it was no drama for you OP.
But the other 1 billion+ peri & post-menopausal women on the planet are likely to benefit from knowing the full likely symptom list, how this MAY affect them, and what the medical & lifestyle approaches which are COMPLETELY DIFFERENT FROM THE APPROPRIATE MEDICAL TREATMENT OF MEN THE SAME AGE are, which may help them the most as they live through this significant life transition.
HTH?