Unlike shared or VPS hosting, dedicated hosting makes your website the lone tenant on a server. To extend the housing metaphor, having a dedicated server is like owning your own home. The means that your website taps the server's full power, and pays for the privilege. If you're looking for a high-powered site—an online mansion for your business—dedicated hosting is the way to go. That said, many dedicated web hosting services task you with handling backend, technical issues, much as homeowners have manage maintenance that renters generally leave to their landlords.
It shouldn't come as any surprise that, like other web host providers, A2 Hosting's unlimited plans aren't actually unlimited. It expect you to use its service like "similarly situated customers." This is like being on a highway. If everyone is going a few miles above the speed limit, you're probably okay, but if you're barreling down the fast lane past everyone else, you're probably going to be asked to slow down.