Hangouts, Meet and Chat are all the apps involving interaction in G Suite, but Google now offers overlapping functionality in these apps. This is because Meet and Chat will eventually replace Hangouts.
When can I use Hangouts?
When chatting with either a UiO user who does not have a G Suite account or with users outside of UiO. The users you are chatting with must have a Google account.
When can I use Meet and Chat?
If you want to arrange a meeting or a chat with a UiO user who has a G Suite at UiO account.
UiO has not activated the GMail or calendar function in G Suite. This is because Outlook Exchange is the preferred e-mail and calendar service at UiO. THis means that services in the Hangouts menu, like Send e-mail or Schedule event can not be used.