Bundler is a tool that makes it easier to keep track of what Ruby gems (and what versions of those gems) an application depends upon
RVM (Ruby Version Manager) is a command line tool which allows users to install, manage and work with multiple Ruby environments from interpreters to sets of gems easily in the various Unix-like systems (such as Linux and Mac OS X).
"Rvm supports more then just .rvmrc one of this files is gemfile with either the bundler directive to specify ruby"
from question "Why is rvm changing paths without an rvmrc?"
"Bundler is a better way to manage application dependencies. there is a plugin rbenv-gemset for getting the same results as rvm s gemsets but sam clearly favors using bundler instead"
from question "Rbenv: Surviving without gemsets"