By default, you will be able to see whether someone is free or busy. To see further calendar details, the calendar owner must first grant you permission by sharing the calendar with you.
Watch a video helplet about Sharing Your Calendar.
Apple Mail, Calendar, and Contacts come with the Macintosh operating system. If you're using a Mac, they should already on your system. These programs can work together on your Mac to provide an integrated email and calendar experience similar to that in Webmail.