How can I build my app for android platform on my mac?
By installing the Android SDK and running ionic cordova build android from your CLI. Look at the platform guide for Android here https://cordova.apache.org/docs/en/latest/guide/platforms/android/ to get some pointers.
so it’s the same as on windows??? and for android emulator?
See the part about genymotion over here: https://ionicframework.com/docs/developer-resources/developer-tips/