Hi JK,

I don't work on any of these parts of Cloud Foundry but I can give a very
basic overview:

[1] rootfs: the filesystem used for applications deployed on Cloud Foundry.
The current default is cflinuxfs2, based on Ubuntu 14.04

[2] garden: "A rich golang client and server for container creation and
management with pluggable backends for linux, windows and The Open
Container Initiative Spec". Garden is running on the Diego cells where
Cloud Foundry applications are run.

[3] stemcells: The base image for VMs deployed by bosh.


Highly recommend staring with the Cloud Foundry documentation:
http://docs.cloudfoundry.org/. You can also "kick the tires" by trying one
of the hosted versions of Cloud Foundry:
https://www.cloudfoundry.org/learn/certified-providers/


Nick


[1] https://github.com/cloudfoundry/stacks
[2] https://github.com/cloudfoundry-incubator/garden
[3] http://bosh.cloudfoundry.org/docs/stemcell.html