To control DMX equipment with your computer, you need some kind of connection between DMX lights and your computer. You need device that can “translate” computer commands to DMX commands. These devices are usually called DMX interfaces.
The most basic DMX interface is simple. You have input – like RS232 or USB and output – 3 pin or 5 pin XLR for DMX signal. In some cases you have additional power supply. Lighting software sends commands to interface via selected port and interface converts them to DMX signals.
Less expensive variants of DMX interfaces use more computers’ CPU power. Basically, computer “thinks” for them.
More advanced versions of DMX interface can operate without computer. These may not look as important, but if you have some problem with your laptop, DMX equipment will continue to work in predefined schema.
There are many types of DMX Interfaces on the market. However, the most popular are USB DMX interfaces.