system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When measuring the blood pressure nurses often say numbers like"120 on 80". What exactly do those numbers mean and why do you die when they coincide?
gpt
The first number is the systolic pressure (when the heart is actively pumping), and the second number is diastolic (when the heart is resting).

120 over 80 is the a borderline healthy measurement on the high side.

High blood pressure is bad because it puts an undue strain on your heart, and comparing systolic and diastolic numbers can help determine exactly what the problem is.