ESRI ArcGIS on a Mac
To run ArcGIS 10.x on an Apple Macintosh computer, the Mac must be set up to run Windows. There are several ways to do this, but they require one of two installation options and a Windows OS license.
Option One: Create a dual-boot setup on your Mac, which allows you to boot into either Mac OS or Windows OS. The typical method for this is to use the free software BootCamp.
Using BootCamp: http://www.apple.com/support/bootcamp/
Option Two: Create a virtual machine on your Mac, which allows you to run an installation of Windows OS in parallel with your existing Mac OS, and to switch from one to the other without booting into either one separately. Typical choices for the virtualization option are the licensed software Parallels or VMware or free Virtual Box from Oracle.
Using Parallels Desktop for Mac: http://www.parallels.com/products/desktop/
Using VMware Fusion: http://www.vmware.com/products/fusion/
Using Virtual Box: https://www.virtualbox.org/wiki/Downloads
Keep in mind that ESRI does NOT support ArcGIS for Mac, and that you can only use ArcGIS within one of the Windows OS installation options described above.
Microsoft provides Windows 10 to students for free, see this store: http://ucsc.onthehub.com