What is Office 365?
Office 365 is a service & software suite provided by Microsoft for you to use. With your subscription you get the latest version of Office, OneDrive storage, plus Office Mobile apps so you can get things done anywhere.
You get the latest version of Office to install on your PC or Mac (on a total of up to 5 computers, since your school laptop counts as one - that's 4 additional computers you can install it on). As of writing that's Office 2019, and you will also continue to get small updates over time. Using OneDrive in addition to autosave, you can start editing a document on one device and pick it up and start editing immediately on another.
Office 365 also provides OneNote, SharePoint & Teams which enable you to collaborate and edit documents in real-time.