Just setting up my dev environment on my new mac and just want someone to clarify all this info if possible for me.

So OSX comes with a standard version of Ruby preinstalled

I install RVM to allow me to install multiple versions of Ruby - I set 1.9.3 as default.

Ok, that's fine up to here.

Now, I have seen a ton of sites saying that RVM uses gemsets to allow me to install different versions of rails into each gemset. Ok but what I get confused with is if I create a new rails app it gets a gemfile and I add the names of my gems into there and use bundle install to install them.

I'm just getting super confused as to how this all fits together.

Is someone able to help me clear up my confusion?

Kind regards,
Neil