The first one is a firewall that operates at the application level. As an HTTP(s) proxy, it probably sends the entire request to the proxy, which filters them all before sending them to your website. Your server's IP will be completely concealed from the internet if the business you're considering buying uses an http proxy. It's the simplest option for protecting your websites that "simply works."
Their base plan includes a Layer 7 barrier (which I understand to be HTTP, HTTPs, etc.), but their advance plan also includes layer 4 coverage (which I understand to be IP and TCP/UDP).
1. Layer 4 firewalls provide the aforementioned functions, as well as the capacity to monitor current internet connections or allow/refuse traffic based on the condition of those connections (i.e. stateful packet investigation).
2. Layer 7 firewalls (also known as application gateways) can perform all of the aforementioned functions, as well as analyze the network packets' contents intelligently. For example, all HTTP POST queries from Chinese Ips could be denied by a Layer 7 firewall. However, the finer the granularity, the slower the system will be.
Since their pricing scheme doesn't match their definitions, I believe they're referring to your VPS's software firewall as "Layer 7," which is technically inaccurate. Consider pintables and Windows Firewall as examples. By paying a little bit more, you can have your VPS behind such a real network firewall. Maybe.
This raises doubts about their expertise across the board if they can't even be bothered to describe their VPS solution using suitable terms to potential clients.
