a company that stores the pages and pictures and other files of your website
a company that stores your web pages on its SERVER, so that they may be accessed from anywhere by anybody on the internet
a company that will serve the files/webpages that make up your website
A company which makes webpages available on the World Wide Web, usually as a commercial venture.
A company charging a monthly fee to host your website on their server to be viewable on the internet. If you want to have a website, you need metaphorically "rent space" from them for your site to be on the internet. A good webhost should provide you with a complete report of statistics for your website and be readily available should you encounter any problems along the way.