Different models of ESP chips integrate various hardware modules. Even the same type of module may have subtle differences across different chips. ESP-IDF provides a small "database" to describe the differences between chips (please note, only differences are described, not commonalities). The contents of this "database" are defined as macros in the **soc/soc_caps.h** file, referred to as **SoC capability macros**. Users can utilize these macros in their code with conditional compilation directives (such as ``#if``) to control which code is actually compiled.
