So here you are working on your blog, entering a post as you scroll down past submit you see Categories and Tags. These things look very similar yet obviously as two separate things they must be different. Yes. And Yes. They are very similar and very different as well.
History
Originally WordPress had categories. But after a while a category would start to get too many articles and bloggers broke down the categories further. This started creating long lists of Categories. Thus tags were born.

Molina's Green Enchiladas
Categories
Categories are the broad term, they help categorize your posts. You can have long keyword phrases; which is a three or four word phrase, as a category. Create unique to your blog phrase for a category name. A category name could be “Dallas Mexican Restaurants” which is a long keyword phrase or “Mex-Food that Rocks” for something unique. But you can also have sub-categories. This great for “Dallas Restaurants” and the sub-category of “Mexican” or “Italian.”
Tags
You use tags to identify terms related to your blog post. These are terms that help readers of your blog and first time visitors identify the content. Unlike the above categories, you only want to use one or two words as tags. Tags related to the post above could be things like “tortillas, margaritas, live mariachis, green enchiladas, chicken tacos” and other related terms.

Good info MJ. Thanks!
Nice and clear MJ! Now could you please go thru the All-In-One-SEO plug-in stuff…:-)Thanks,Mtn Jim
Nice and clear MJ! Now could you please go thru the All-In-One-SEO plug-in stuff…:-)Thanks,Mtn Jim
Will do Jim! Will actually explain why I am switching to Platinum SEO which is very similar to All in One!