Linux
Linux is the generic term for a UNIX-like open source operating system based on the Linux kernel.

Windows Servers
Windows Server 2022 is the current server operating system from Microsoft.

Apache
Version 2.4 of the Apache HTTPd Server. When asking questions about virtualhosts, please include the output of the following command

nginx
Nginx ("eNgine x") is a lightweight, high-performance HTTP server, reverse proxy, TCP stream proxy and mail proxy, released under a BSD

ubuntu
Ubuntu 20.04, named "Focal Fossa" is a Long Term Support release of Ubuntu Linux (released on April 23rd, 2020).

Centos
CentOS is a free (as in beer and speech) GNU/Linux distribution that is community driven and based on source code released from RedHat.

mysql
MySQL is an open-source database owned by Oracle.

mssql
Questions related to Microsoft SQL Server. If your question is version specific please tag it specifically for that version as well. Does your SQL Server question belong here or on another site? Click the about the sql-server tag link on the line below.

PHP
PHP is a general-purpose scripting language that is especially suited for Web development. The online manual is an excellent resource for the language syntax and has an extensive list of the built-in and extension functions. Most extensions can be found in PECL.

Debian
Debian is a popular and influential GNU/Linux distribution. Questions here should generally be about Debian Server.

IIS
IIS is Internet Information Services, the web server included with Microsoft's Windows Server operating systems. This is a generic tag. Wherever possible please use a *version-specific* tag, such as [iis-7], [iis-7.5], etc.

Raid
RAID, an acronym originally for Redundant Array of Inexpensive Disks (today usually interpreted as referred to as Redundant Array of Independent Disks), is a technology that provides increased storage performance and reliability through redundancy by spreading data across multiple disks using various algorithms (RAID-levels). RAID can be implemented in hardware storage controllers, or in software, usually as operating system/kernel features.

ftp
File Transfer Protocol is a standard network protocol used to transfer data across TCP-based networks between hosts.

Hard disk
Questions about hard disks' performance, issues, tips, and software.

Servers

Mail Server
Refers to the hardware or software that make up a server dedicated to sending and receiving emails. Many popular modern email servers bundle other functionality for contacts and calendaring along email delivery.

Storage Server

Mother Board