I wanted to install Ruby 2.0.0 through rbenv for a project, because they list their Ruby version as 2.0.0. But there are a couple different versions listed there:
2.0.0-previewX are preview releases that may contain some serious issues or features that'll never be a part of the first stable release (
2.0.0-p0). For example,
2.1.0-preview1 had frozen string literals (
'frozen'f) which were later replaced by an optimized
2.0.0-pX are stable releases of 2.0.0.
p means patch (level) and is followed by the number of commits since the first 2.0.0 stable release. Starting with 2.1.0 the version policy was changed and this number isn't much of interest to end users anymore.
To find out which is the most current version of the 2.0.0 series, you can visit the official downloads site.