CVAR and ConVar are abbreviations for Console Variable

Variable (programming)

In computer programming, a variable is a symbolic name given to some known or unknown quantity or information, for the purpose of allowing the name to be used independently of the information it represents...

. Depending on the context in which the term is found, it may also stand for Client

Client (computing)

A client is an application or system that accesses a service made available by a server. The server is often on another computer system, in which case the client accesses the service by way of a network....

 Variable, or Configuration Variable.

This is a type of variable used in many computer games and computer 3D simulation engines

Game engine

A game engine is a system designed for the creation and development of video games. There are many game engines that are designed to work on video game consoles and personal computers...

 that can be manipulated by a text based command line interface within the game or engine, often called a console. They commonly hold configuration parameter

Parameter

Parameter from Ancient Greek παρά also “para” meaning “beside, subsidiary” and μέτρον also “metron” meaning “measure”, can be interpreted in mathematics, logic, linguistics, environmental science and other disciplines....

s, but can be used for anything that may potentially be accessed and/or modified by the console.

The most common usage of CVARs is by server operators to customize their online game server

Server (computing)

In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...

s.