Topic: Where do I find more information about GEM management?

I've been using Rails for about a month and I'm confused about how to do GEM management.
I just ran the command

$ gem outdated

And I got a long list.
I was in the directory for an app on my iMac.
I have a few questions:
1) Are the GEMs installed on my iMac for use by all my Rails apps, or does each Rails app get it's own set of GEMs installed?
2) Does SUDO mean global for all Rails apps?
3) Should I be keeping these GEMs up-to-date or only if I need a particular one updated?
4) If I change the GEM file and remove a GEM and then run Bundle Install - will it remove the GEM from my app?
5) Will #4 also remove it from Heroku, when I push?

Is there a particular article I should read to get these answers?

Thanks !!

Re: Where do I find more information about GEM management?

#1 Gems are universal, they are stored OUTSIDE any rails aware directory structure
#2 sudo is a Unix thing,  it means 'super user do',  it runs the following command as the super user (the root user) on the Unix box.  It temporarily changes the effective id to the super user while the command is executing.  You have to have permission to run the sudo command,  the Unix system administrator would set that up for you. 
#3 If you update a gem,  it doesn't replace the old gem,  it just adds a new version of that gem. 
#4 It will stop THAT app where the Gemfile exists from depending on that gem.  but it won't remove the gem from the system as a whole,  other rails apps that have that gem listed in the Gemfile will continue to operate.
#5 No,  removing a gem from Gemfile will not cause the gem to be removed,  it just tells the rails server that that particular app does not require that gem to operate.

Joe got a job, on the day shift, at the Utility Muffin Research Kitchen, arrogantly twisting the sterile canvas snout of a fully charged icing anointment utensil.

Re: Where do I find more information about GEM management?

Thanks Brad !!