If you wish to publish a personal website, blog or even a professional corporate website of your business, you need to "host it" somewhere online.

A website needs a space on the world wide web , where all files, images and data can be stored in order for the site to appear correctly and be accessible 24h/7 to all web users. 

So, in order to get your websites pages - or just a file - visible online, you need to rent some space from a company that specializes in serving files out across the internet, to "host" your website for you,.