An external graphics card is a device that can be connected to a computer, usually intended for use with laptop computers, to provide graphical output for that computer. There are two basic types of devices referred to as external graphics cards. The first provides a way to connect two or more monitors to a single computer. The other type is a device that can be connected to a computer, to which a graphics card can be connected or installed and provide graphics processing for that computer.
One of the most common types of external cards is a device that can be connected to a computer, which allows that computer to then be connected to multiple monitors or displays. These cards are used for a number of different reasons, often to create computer work stations in which someone can be using a program on one monitor, while viewing other information being displayed by the computer on another monitor. This type of graphics card can also allow the user to have his or her computer connected to a monitor he or she is viewing, while also connecting to a larger display for others to see what he or she is doing for demonstration or seminar purposes.
The benefits of this type of external graphics card are that it is usually fairly inexpensive and can be helpful for users with a graphics card that does not innately support multiple displays. Due to the fact that this type of device is usually connected to a computer through a universal serial bus (USB) port or similar connection, however, there is typically some signal bottlenecking that occurs. This means that the data sent through this type of system is limited by the USB connection, so these devices are not truly used as external graphics rendering systems.
An external graphics card that is actually used to render and display graphics for a computer, however, is available from a few manufacturers. These devices are typically rarer than the other kind and are also quite a bit more expensive due to the functionality they provide. This type of graphics card often serves as a container for a separate graphics card that can be installed into it.
The device is then connected to a computer, usually a laptop, and serves to process graphical data for that machine. A separate graphics card is usually needed with this type of external graphics card, which increases the expense of such a system. These devices usually connect to a laptop through a peripheral component interconnect express (PCIe or PCI-E) connection, which eliminates the bottlenecking from USB connections and allows the graphics card to effectively render even highly detailed graphics.