You could think of the sites that share your server as your roommates; there's really not that much separating you from them. Sure, you can close the bedroom door, but they can still cause nightmares for you in the kitchen and the bathroom. In web hosting terms, all the sites share a single server's resources, so huge traffic spike on Site A may impact the neighboring sites' performances. It's even possible that another site could take down the shared server altogether, if it crashed hard enough.
As with backups, SSL certificates are not a necessary feature your web host must offer, this is especially so since companies like Let’s Encrypt offer them for free. However, if you’re looking to streamline the process of getting your site fully equipped and online in no time, the extra convenience of getting this certificate from your web hosting provider is a nice add-on.
Also known as a Virtual Private Server (VPS), divides server resources into virtual servers, where resources can be allocated in a way that does not directly reflect the underlying hardware. VPS will often be allocated resources based on a one server to many VPSs relationship, however virtualisation may be done for a number of reasons, including the ability to move a VPS container between servers. The users may have root access to their own virtual space. Customers are sometimes responsible for patching and maintaining the server (unmanaged server) or the VPS provider may provide server admin tasks for the customer (managed server).
These services can host your content on their servers free of charge, but in exchange for that zero cost, your online destination will have a less-than-elegant domain, such as jeffreylwilson.tumblr.com. That might be fine for a personal blog, but it will look too low-rent for a business that wants people to trust it enough to pay for whatever it's selling. HTML Full Course - Build a Website Tutorial