The binary files to install.
.PKGINFO: contains all the metadata needed by pacman to deal with packages, dependencies, etc.
.MTREE: contains hashes and timestamps of the files, which are included in the local database so that pacman can verify the integrity of the package.
.INSTALL: an optional file used to execute commands after the install/upgrade/remove stage. (This file is present only if specified in the PKGBUILD.)
.Changelog: an optional file kept by the package maintainer documenting the changes of the package. (It is not present in all packages.)