# 5.2. Definitions

- Source tree: The tree where the PMIx source code is located. It is typically the result of expanding an PMIx distribution source code bundle, such as a tarball.

- Build tree: The tree where PMIx was built. It is always related to a specific source tree, but may actually be a different tree (since PMIx supports VPATH builds). Specifically, this is the tree where you invoked `configure`, `make`, etc. to build and install PMIx.

- Installation tree: The tree where PMIx was installed. It is typically the “prefix” argument given to PMIx’s `configure` script; it is the directory from which you run installed PMIx executables.