Modules are a way of grouping and separating concepts in our application. Modules should be named following the Ubiquitous Language. We shouldn't forget that modules are a way to communicate high-level concepts, which aids us in keeping coupling low and cohesion high. We've seen that we could create meaningful modules even in old versions of PHP by using prefixes. Nowadays, it's easy to build our modules following the PSR-0 and PSR-4 namespacing conventions.