This is 1 in

This is 5 cm

This is 16px

This is 2em

This is 2em (div font-size = 20px * 2 = 40px)

This is 2rem (HTML font-size: 40px) *2 = 80px

This is 200%

This is 200% of the parent.

This is 20vh

This is 20vw

This is 160px