Configuration files, which are denoted by the .conf extension, define various configuration variables that govern the project's build process. These files fall into several areas that define machine configuration options, distribution configuration options, compiler tuning options, general common configuration options, and user configuration options.

Class files, which are denoted by the .bbclass extension, contain information that is useful to share between metadata files. The BitBake source tree currently comes with one class metadata file called base.bbclass. You can find this file in the classes directory. The base.bbclass file is special since it is always included automatically for all recipes and classes. This class contains definitions for standard basic tasks such as fetching, unpacking, configuring (empty by default), compiling (runs any makefile present), installing (empty by default), and packaging (empty by default). These tasks are often overridden or extended by other classes added during the project development process.

BitBake recipes, which are denoted by the .bb file extension (for example, bcm2835_1.38.bb ), are the most basic metadata files. These recipe files provide BitBake with the following information: