sapui5 what is a pixel?

Hi guys,

What is a pixel in SAPUI5? I'm asking this because in the WEBIDE (when running the app in the frame that allows changing of the orientation and resolution) one has the option 800x600, etc. I have no smartphone that has such a low resolution. My laptop has 2000+ pixels so how is this interpreted by SAPUI5 in terms of "pixels".

I'd appreciate a link to the official documentation (which I couldn't find).

Kind regards, Ioan.