These days, we're all scheduling way more online meetings than ever before. Using Appoint.ly cuts out a few steps in that process, allowing for external audiences to view your schedule and pick a timeslot. Internal colleagues could, of course, use it as well, but we use Outlook for scheduling our internal meetings so there's no need to use this, too. So it's basically a way of letting external people access your Outlook calendar so they can find mutually convenient times to schedule meetings, without a lot of back-and-forth conversation required to do so. Review collected by and hosted on G2.com.
It took me a bit to figure out how to integrate it with my Outlook calendar. I'm doing it through my work account, but it tried to log me in by default through a hotmail account that I also access occasionally through that computer. I obviously don't do a ton of meeting planning via hotmail. I thus had to connect it to my work Outlook instead. This took a little while to figure out, though it's entirely possible (if not likely) that that was due to user error/ignorance rather than anything having to do with the software or its integration capabilities. Review collected by and hosted on G2.com.