Using tags in All In One SEO pack

Hi,
I am using All In One SEO pack to optimize my pages. But i have one question that i’m not sure and i cannot find the solution in the internet.
My question is: Do i need to add tags after writing my pages? I see some videos in youtube, but they seem not care about the tags. They just add title, description and keywords only.

So i would like to ask if it affect ranking?

I notice that when i add tags, actually each tags will produce one more URL link to the same post, so is this an issue with adsense?

Thank you very much for helps