The Domain Name System matches the URL-address of your website or service and the IP-address of the server or the virtual machine, where it works.
Secure Sockets Layer and its successor Transport Layer Security are cryptographic protocols that secure communications between your customer web browser and your server.
A numeric status code (such as "404") that indicates the health of the web-server or availability of the requested resources.
A textual reason phrase (such as "Not Found") in the first line of the HTTP response (the status line) that describes the numeric status code.
The time between user's request of the webpage from your server and the moment he/she gets it.
Ping is a program to send test packets to your server and count the time till its answer.
Your server runs a lot of services on different ports, e.g. 80 for HTTP or 443 for HTTPS (HTTP over SSL/TLS)...
Traceroute is a program, that shows how the data (or request) travels over the world.