Default browser for Mac OS is Safari. You can also install other browser like Google Chrome or Mozilla Firefox.
Usually to install an app in Mac, through App Store, but for Google Chrome browser at this time there is no Chrome in App store.
The solution to install Chrome browser in Mac OS you can go to Chrome website and download the installer (googlechrome.dmg)
Open the browser (Safari) and search for Google chrome to get to Chrome website. then choose Download. It will automatically detect the Google Chrome for Mac.
After download, double click the file installer (googlechrome.dmg) located at download folder.
There will be a warning like: "Google Chrome" is an application download from the Internet. Are you sure you want to open it? choose open.
After installed you will see the Google Chrome icon in Launchpad..