It will give you access to advanced features, such as: the When view (Gantt chart), the Who view (team schedule) and 3 multi-projects views.
To read about the terms and prices of the different subscriptions, see this page.
With a Business subscription, you can also subscribe for other users.
The Business subscription can only be taken via the web application.
You can choose to take a monthly or yearly subscription. The yearly subscription entitles you to a discount.
To display/change your current subscription, see this page.