What is it?
Serverless hosting is not actually serverless. It is just that another company manages the servers for the website.
Reasons to use
Managing servers is a whole other job outside of development. Servers are expensive to maintain for large amounts of data. Using a web host gives the developer time to focus on the website or application without the hassle of managing servers.
Amazon Web Services
Amazon already has a large staff managing their servers. Why not let them manage yours. They have tutorials to get you started and tons of support.
Parse Server
This is an open source option. They have a blog with lots of info. If you like them and want to help there is a link to back them.
Summary
I found large and small options for serverless hosting. They are scalable and provide support. As always it is best to research before making the choice to go with a serverless hosting option.