Css, html class selectors, and id's

I’m new to this forum and to html and css. I understand the structure of both html and css in general. What I don’t understand is basically how you decide what is a class, what is an id, and how you are supposed to name them as such. I saw an article named"[h=1]CSS Selectors: Type, Class, and ID[/h][COLOR=#808080][FONT=Arial]by kirupa | 6 June 2012" that almost explained everything clearly. I think if I could just get to the crux of either how to name these things or how to write the code for them I’d be well on my way to understanding and being able to produce some good pages. Right now, everything just seems like a foreigh language and it seems every thing I read takes a lot for granted and seems to be leaving out important information. Or it could be that it’s all staring me right in the face and I just can’t see it yet. Is there any help out there for somebody in my position?

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