Website hosting is the service you pay for to serve web pages to visitors. In the case of WordPress your hosting consists of one or more MySQL databases and thousands of files that make up your Content Management System (CMS). Think of it as a lease on server space and reliable throughput. Without it, your website cannot be displayed to visitors.
Security maintenance is a specific requirement of using WordPress for your CMS. WordPress requires maintenance to remain secure and up to date. Entrusting this activity to 3PRIME means that you can rely on consistent performance for your WordPress website, but you must still maintain your domain name as well as web hosting services.