A server is essentially a computer or hard drive “out there” that hosts your website files. Just like your computer has files on that you can access and interact with, a server hosts your website files that you and your users can interact with.
Your hosting company provides you with the server for your website.
Not all hosting companies and servers are created equal. You will find a lot of options and pricing company to company. If you’re having trouble with your host, you might need to find a new one.