I want to display my website in Mobile friendly layout when opened in any mobile phone

Dear folks,
I have a website xyz.com and usually it is opened in browser on desktop systems. I want it to be opened in mobile friendly layout when opened in a mobile phone's browser. For example, you would have noticed that when you open yahoo.com in your phone's browser, it redirects to m.yahoo.com and yahoo does not look same as desktop's browser rather it fits in mobile's screen. How can i achieve this?
Thanks