Mail merge is a feature in Microsoft Word that allows you to create personalized documents, such as letters, envelopes, or labels, by combining a main document (containing generic content) with a data source (such as an Excel spreadsheet or a database) that contains specific information for individual recipients. This feature is commonly used for creating mass mailings or personalized communication materials.

The built-in memory of a computer typically refers to RAM (Random Access Memory). RAM is a type of volatile memory that the computer uses to temporarily store data that is actively being used or processed. It provides fast access to the data the computer needs to perform tasks, and its content is erased when the computer is powered off.

The "@" symbol is used to separate the username of an email address from the domain name of the Internet Service Provider (ISP) or email service provider. For example, in the email address "username@example.com," "username" is the username of the email account, and "example.com" is the domain name of the email service provider, separated by the "@" symbol.

An output device that is used for TV-like displays and shows the output on the screen is indeed called a monitor. It is also commonly referred to as a visual display unit (VDU). Monitors and VDUs are used to display visual information from computers and other electronic devices, allowing users to view text, images, videos, and other graphical content. They come in various types, including CRT (Cathode Ray Tube), LCD (Liquid Crystal Display), LED (Light Emitting Diode), and OLED (Organic Light Emitting Diode) monitors.