Microsoft Teams

Microsoft Teams is "the best messaging application for your organization — a workspace for real-time collaboration and communication, meetings, file and app sharing". It includes chat, video calls, file storage and app integration into one platform to make remote collaboration seamless so you should use it.

Teams can be used by anyone with a Microsoft 365 license. You must have a license of one of the following: Business Essentials, Business Premium, Enterprise E1, E3 or even E4 & E5. Also, free versions are available with limited features.

A team is defined as a "group of people who you’ve assembled to get something really big and important done in your organization". Channels are, according the company itself, "the conversations you have with your teammates," each covering a predefined topic department or project.

You can close channels and chats that you are not using, disable auto-start in Settings option, enter meetings only in audio mode (which reduces memory usage by almost 30%), clear the Teams cache — for example deleting files.

Yes, you can view historical chat messages and previously downloaded files while offline. All actions will automatically sync once you reconnect to the internet.