The Source Directory includes a copy of BitBake for ease of use. The copy usually matches the current stable BitBake release from the BitBake project. BitBake, a metadata interpreter, reads the Yocto Project metadata and runs the tasks defined by that data. Failures are usually from the metadata and not from BitBake itself. Consequently, most users do not need to worry about BitBake.

When you run the bitbake command, the wrapper script in scripts/ is executed to run the main BitBake executable, which resides in the bitbake/bin/ directory. Sourcing the oe-init-build-env script places the scripts and bitbake/bin directories (in that order) into the shell's PATH environment variable.

For more information on BitBake, see the BitBake documentation inculded in the bitbake/doc/manual directory of the Source Directory.