Are Safari and Google Chrome the same?
They look almost the same. Do they display pages the same. How can Google get away with this? Because I can hardly tell the difference.
MacBook Pro with Retina display, OS X Yosemite (10.10)
They are browsers.
They have browser engines AKA layout engines. If they "look almost the same" it is because the guts of these browsers (e.g. Safari, Firefox, Google Chrome, Sea Monkey, Opera and so on) use their particular layout engine to display a particular web page from a particular serve written in a particular set of HTML or other instructions.
They way the web page appears to you on your computer is a function of what the designer of the web page intended the visitor to that webpage to see, and how well the browser (e.g. Safari, Firefox, Google Chrome, Sea Monkey, Opera) interpret the instructions on the web page AND how you have your own browser configured.
See
http://en.wikipedia.org/wiki/Web_browser
http://en.wikipedia.org/wiki/Web_browser_engine
Try Sea Monkey sometime, you will be pleased at speed of it.
http://www.seamonkey-project.org/releases/seamonkey2.31/
Going back to your question - ideally, browsers would present to you the view of what the webpage designer intended so they should look somewhat the same. Where differences occur is due to rendering speed, addons, plug ins etc.
An (inadequate) analogy might be a set of reading glasses or binoculars. You can look at the world through a pair of Bushnells, Nikon, or Zeiss. Ideally they would bring back the same image.