Hello, and thank you for using this service.
Office 365 is the new online version of Office. It has many extra features and advantages over the standard desktop office. These include constant updates so you are always using the latest version and features, and also cloud based backup. The disadvantage is that there is a monthly fee in cost, but the advantage over the desktop is that you can try it 30 days free, and there is no larger up front cost.
Since Office 365 is free for the first month, you might want to simply try it to see if you like it, and then you can consider continuing with it, or purchasing the traditional desktop office 2016.
Do you have any other questions on this?