While I cannot explain OOP to you in a maner that you could understand in a simple paragraph or two I can point you to some resources I have found valuable.
First I would suggest using the Starter kit for VS2005 to begin building your modules, I found a great step-by-step tutorial at the following URL http://www.adefwebserver.com/DotNetNukeHELP/DNN_Module4/Default.htm
And here is a link to Microsoft MSDN on OOP programming for VB.net http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dv_vstechart/html/vbtchooinvbnet.asp
Just remeber a Class is like a blueprint to building something i.e a house, and an object is a House that was built using the Class (or blueprint) you can build as many houses (objects) as you want using the same blueprint, or you can modify the blueprint (by inheriting the class) and add new things.
If I may I want to point you to a final resource I have used to ramp up to programming in .net it is a website that contains 60+ hours of videos on progamming in .NET there is a very minimal cost when you figure in the amount of training contained in all the videos. My friend and I were on a contract VB assignment that was 2 hours away, so we downloaded all the videos to our laptops, and we watched and listened to the videos while we would take turns driving back and forth to our assignment. In about a month we had absorbed quite a lot of the .Net and we were able to make a hasty transition into new .net careers. The url is www.LearnVisualStudio.net
Good luck and I hope this helps. 