Puppet 3.8.1 is a bug fix release (with future parser changes) in the Puppet 3.8 series. It’s first official open source release in the 3.8 series.
The main focus of this release is to make sure the 3.8 future parser is forward-compatible with the Puppet language as of Puppet 4.1. It also fixes several bugs.
Check out the release notes for more information:
https://docs.puppetlabs.com/puppet/3.8/reference/release_notes.html#puppet-381
You can see the full list of changes on the release's JIRA page:
https://tickets.puppetlabs.com/secure/ReleaseNote.jspa?version=13116&styleName=&projectId=10102
If you're installing Puppet for the first time, follow the Installation Guide: https://docs.puppetlabs.com/guides/install_puppet/pre_install.htmlc