Shared hosting is like an apartment building where the building or server has many tenants or hosting accounts sharing the space and the utilities. This works just fine if you have a small family but if everyone in the building has ten roommates move in who are constantly running the water and using the wifi then the water pressure and wifi speed start to suffer. The key to shared hosting is that it is meant for small business websites, sure you can pack the roommates or files in like sardines but it will really be uncomfortable.
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.