Eclipse extention point confusion

[Dinesh Bang]

Hi Ranchers,

I have a confusion regarding when to create a new Extention point and contributor.

And details or a link to good article will be helpful.

Also , in case I have a UI tree to display (like the project explorer) in one plugin and I have the children or nodes which will be displayed are present in other plugin. Will it be a good idea to use extention point and contributor between the two plugins ?