A review must have a corresponding product subtype. The tags for a review are simple enough though.
--- reviews: im2000: description: The best bit of weight-training kit I've owned. It has a compact footprint yet it contains a Smith machine, high/low pulley system and supports free-weight exercises. Great build quality too. rating: 5 ---
Note in the example above, the im2000 review tag must match a product tag of the same name.
The description in a product is basically just what it is, the description in a review is your opinion of the product.
Ratings are between 0 and 5 in half-star increments.