Many services offer so-called unlimited or unmetered service for whatever amount of bandwidth, disk storage and sites you use. It's important to understand that most terms of service actually do limit the definition of "unlimited" to what's considered reasonable use. The bottom line is simple: if you're building a pretty basic website, unlimited means you don't need to worry. But if you're trying to do something excessive (or illegal, immoral or fattening), the fine print in the terms of service will trigger, and you'll either be asked to spend more or go elsewhere.
Dedicated hosting is not for everyone and generally provides more resources than the average business requires. Dedicated hosting is ideal for very large companies that regularly experience a high volume of internet traffic or sales, or require a large amount of disk space. Dedicated hosting grants you the greatest flexibility, customization, and security of the three types of hosting but is also the most expensive.
Why should you upgrade to a VPS or Dedicated Server? This may have to do with the type of site you have. If you have a lot of photos and videos that are password protected, this may be against your host’s rules for shared accounts which often prohibit file storage. Or you have a lot of site visitors, the metaphorical guests in your apartment, and your account may start getting crowded as those guests start clogging up the “hallways” otherwise known as CPU capacity. Another reason is to have full control over the configuration of your server, if you own a house you can make modifications you may not be allowed to make in an apartment or townhome.
Almost all the services offer some sort of page builder that makes it easy to drag and drop to build your page. These are great for getting started, but they often lock you into the service. Most page builders are proprietary to the service, or don't create HTML that's portable enough to be easily moved to another service if you decide it's necessary.