Manged WordPress Hosting is when an external site takes care of your site making sure it is both secure and fast.
This is when you get an external company to take care of all your hosting related issues. This includes all the backups, security checks, updating WordPress and many other things.
Manged WordPress Hosting can help you be more focused on your sites content and performance rather than all the behind-the-scenes technical issues that may come up.
While managed WordPress Hosting can be more expensive it is very helpful especially if you are a new business. This can be due to there being so many things to think about, meaning you may forget some of the background stuff such as updates. Having another company overlooking that can give you peace of mind and less things to worry about.