Hey all, brand new to VB.net

I am learning VB so that I can program Revit, the API chart has a list of the objects I can manipulate but I don't understand the chart yet but will soon enough.

In the chart, what sticks out first to me is Enumerable, Enumerator and Enumeration. No clue to what this is or what it means. Some of the (3) listed above have the letter 'I' as in IEnumerator. (is there a differece? and what is it?)

I did a search and kind of understand that it a group, or catalog or catagory, maybe???

I searched this forum and found some (future useful) information about Enums but my lack of a straight forward definision limits my understanding.

Can someone please explain in non-tech language with a genric explainaiton and maybe a very elementry example so I can build my understanding and derive more useful questions from.

Thanks