Help with docker

Hey guys,

I am a student who is figuring out how dockertoolbox works. I have some questions in my mind whose answers I could not find on the web. Any sort of help would be greatly appreciated .So I know the basics of how docker works (containers hv etc)
(I run docker toolbox on windows 7)

1.When i pull images and run them using docker run , am I running that os and controlling it through the quickstart terminal ?
2.How can I build images of java eclipse,mysql and tomcat myself?
3.For example when I enter the command “docker run ubuntu:14.04” , nothing changes.

Will try to add more questions .

Thanks a ton.