Responsive Designs

Why we use percentage(%) values instead of pixels(px)?
Please explain in brief.
Thank for co-operation

If an HTML document is using fixed sizing in pixel
and displaying on a =notebook= nicely
and _displaying= the same HTML document on a =handy= could be quite off…
So then you might try to use percentage(%) in your sizing…

Apart from percentage(%)
you could use em and or rem

== discussions / operations ==