Just figure out, thought of sharing. (Correct me if i'm wrong) Let say we make a post for Modern Swimming Pool Design... Keywords = modern swimming pool, modern pool, pool design, pool designs, pool idea, pool ideas * Purpose of keyword is to tell search engine what is this post about. Category = Home Design - Exterior Design (assuming it's under a Exterior Design category) * Purpose of category is to setup a good structure for the website. Tag1 = modern design (you may make more than 1 modern pool post) Tag2 = pool design (you may make more than 1 pool design post) * Purpose of tag is to combine and link posts talking about same thing. For example you have 10 posts in Exterior design. 3 of them talk about pool design and 2 of them talk about modern design. This is how you link them together.