Skype is included with the university's Office 365 subscription, and all Active Directory users can access and be contacted via Skype. We sometimes use it for within- and between-department communication, especially for quick instant messaging. Skype is, of course, one of the original household names in videoconferencing, etc., but we don't use it much for that on a daily basis.
Microsoft Teams seems to do everything that Skype does, but allows for much more collaboration with Office products, is much less clunky, and is much more easy to understand, seemingly. For videoconferencing, especially with offsite or non-organization users, Zoom is unrivaled in my opinion. It's lightweight, easy for everyone to use, and has great options for collaboration and sharing.
Skype has been around long enough that there's quite a lot of resources available online, including from Microsoft. However, this can also be problematic since it's been through so many versions, and sometimes support for one version or iteration of Skype is totally irrelevant for the most recent version. This has improved recently as Microsoft has worked to unify their apps, but there's still plenty of room for improvement.
Skype is pretty good as an integrated tool for quick communication between departments. However, Zoom is lightyears ahead of Skype (and everything else we've tried) as a videoconferencing solution. Teams (another, newer Microsoft product) works for all the things I like about Skype namely within-organization collaboration and communication and is more streamlined and tightly connected to the Office suite in ways that Skype is not.