Unlike VPS hosting, which is limited by the physical server on which your website is hosted, cloud hosting allows you to use resources offered by multiple machines. For example, if you find that your website is lagging because of lack of bandwidth, you can increase the amount available to you. Often, you can make this change yourself via the host's control panel.
Moving to another website consists of transferring the website’s files and databases, configuring your site with the new host, and directing your domain’s DNS to the new host. Once you pick a new site host, they can usually help you out with this process. The cost will depend on the host you’re switching to, but it will probably be anywhere from $150-$400.