There are a number of tools available that enable you to chat or meet online with colleagues at the University of York or external parties. It very much depends your preferences and those of your wider team and collaborators.
Hangouts is an instant messaging tool with the added features of voice and video calling. Hangouts Chat is for team messaging and Hangouts Meet is for hosting video meetings. The IT services webpages contain Guidance on Hangouts, Hangouts Chat and Hangouts Meet.
An advantage of using Hangouts, Hangouts Chat and Slack over Gmail are that they can offer a reduction in email overload. As chat tools offer a more informal method for communication you may find some colleagues will respond quicker to these kinds of interactions than they would via email. Email overload is a very real challenge and UoY tips on Email etiquette and email usage propose the use of Google Chat tools as a viable alternative.