This package was previously used to provide a number of features that were useful for typesetting documents with XeLaTeX. Many of those features have now been incorporated into the fontspec package and other packages, but the package persists for backwards compatibility. Nowadays, loading xltxtra will: load the fontspec, metalogo, and realscripts packages; redefine \showhyphens so it works correctly; and define two extra commands: \vfrac and \namedglyph.