CIDR (Classless Inter-Domain Routing) is a network protocol that enables more efficient use of the network addressing system on the Internet and other networks. CIDR was created to overcome the limitations of the traditional classful addressing system.

HTTP/2 (HyperText Transfer Protocol / 2) is a protocol that is an improved version of the HTTP/1.1 protocol, released by the HTTP Working Group in 2015. HTTP/2 is supported by most modern browsers and allows web pages to load faster than previous versions.

DNS connects domain names (domain names) to IP addresses. The DNS PTR record, otherwise known as the pointer record, provides the domain name associated with the IP address. A DNS PTR record is the exact opposite of an "A" record, which specifies the IP address associated with a domain name.
When a user tries to access a domain name in their browser, a DNS lookup occurs in the background, where the system looks for the IP address associated with the domain name. And DNS PTR records are used in reverse DNS lookups, which is the exact opposite of the normal DNS lookup process: it's a query that starts with an IP address and finds the domain name associated with it.

HSTS (HTTP Strict Transport Security) is a policy mechanism that helps protect websites from man-in-the-middle attacks, such as protocol downgrade or cookie hijacking. It allows websites to require web browsers (and other web client applications) to automatically only use HTTPS connections, which implement strong encryption using SSL/TLS. HSTS is a 2012 IETF standard defined in RFC 6797.

The Universal Naming Convention (UNC) is a naming standard for identifying servers, printers, and other network resources that originated in the Unix community.

Uncomplicated Firewall (UFW) is one such frontend of iptables and is particularly suitable for server-based firewalls. Ufw provides a framework for managing netfilter, as well as a command-line interface for managing a firewall that uses few and simple commands. Ufw is designed to provide an easy-to-use interface for those unfamiliar with firewall concepts, while simplifying complex iptables commands to help administrators who know what they are doing. UFW is also an upstream software package for other distributions and graphical frontends.

In all Linux distributions, programs that can be installed on the system are distributed as software packages. Software packages are typically a set of data packaged in a file that contains the software itself, as well as a number of additional information (metadata) about the software, such as package descriptions, installation scripts, dependency data, and so on. Linux distributions maintain their own repositories, into which software packages can only be accessed after strict checks. Packages consist of a package database containing package information and an organized structure of downloadable binary package files.

Debian in its stable version offers the use of stable packages by default, which can be used to build extremely reliable systems. The packages in it have been tested as extensively as possible, so there is almost no chance of anything going wrong with them. However, this has the disadvantage that in many cases the packages are not up-to-date, so it is often the case that newer versions of the same packages are available in other Linux distributions. Debian offers the Backports repository to remedy this.

The Master Boot Record (MBR) is a special boot sector at the very beginning of partitioned computer storage devices. Examples of such devices are built-in or removable hard disks, SSDs, flash drives. The MBR concept was officially introduced in DOS version 1983 of the PC in 2.0 and has been running on used BIOS personal computers even today.

A GUID partition table (GPT) is a standard for arranging partition tables for physical computer storage devices, such as hard disk drives or SSDs, that uses universally unique identifiers (UUIDs), also known as GUIDs, to clearly distinguish partitions on a storage device. . GPT is part of the Unified Extensible Firmware Interface (UEFI) standard.