I don't really understand the difference between phpBB2, phpBB3, punBB, Invision. Can someone explain what they mean? and which one would be best to use for customization purposes?

Hi!

Basically, these are different types of forum softwares which can be used on any site to set up a discussion board facility.

http://phpBB.com | http://invisionpower.com | http://punbb.informer.com

Forumotion provide free hosting of the above softwares. We can switch between then at any time via Admin Panel. For customization purpose all the versions are good.

phpBB2 has old styled tabled layouts but it has a plus point of template editing. phpBB3 doesn't have template editing but it has a neat and sleek design. punBB comes with simple look and ability to edit the templates so its really good while Invision doesn't have template editing but a nice layout.

There are many other forum softwares though Forumotion doesn't provide hosting for them : http://www.forum-software.org/

If I would like to customize a large part of the site using coding which one would be simplest to use yet very versatile?

punBB is best for large customization.

Thanks man