Eurorack is a modular synthesizer format that allows musicians and sound designers to create custom synthesizer setups. It consists of various individual modules that can be connected using patch cables, enabling users to design unique soundscapes and effects. Each module typically serves a specific function, such as oscillators, filters, or sequencers. The standard size for Eurorack modules is 3U in height and varies in width, measured in "HP" (horizontal pitch). This format has gained popularity due to its flexibility and the vast array of available modules from different manufacturers, allowing for endless creative possibilities in electronic music production.