Two types of categories

You can create those categories. You'll see the option in the post section of WordPress.

Then, use the widgets options under appearance and set up your categories on the sidebar.

This might differ based on your theme too, so do accordingly. Hope that helped.

@ aarthielumalai: My question is different. Please read it carefully.

If I understand you correctly, you want your posts to show up in both categories? If so, simply checkmark both boxes when you choose the category to post your reviews in.

I hope that answered your question.

Thanks Denise & Aarthie.

(i) My question is different. I want posts to appear under two categories titles in side bar. Category title 1: ABC & Category Title 2: XYZ.

(ii) Both the main categories will have different sub-categories.

OK, we will have to start to use the proper language (WP terminology) to make sense of your question!

1. "Category" is a specific thing in WordPress = every post you create must be in a category - there are no post outside of categories.
So, unless we are talking about WP created categories (the way how we group posts).... STOP using the word category

Assuming we talk about WP intrinsic categories and not some general term:

2. Also not clear: you want to list POSTS in the sidebar or SUBCATEGORIES? Unless, the latter one - it is irrelevant whether the categories have subcats or not.

3. Continuing with the assumption of WP cats... you would place those posts in each category where you want them to show up. Then you need to build a new query to retrieve those posts to show up in the sidebar.

4. There is an old plugin (not updated for about 2-3 years) to do it.
You can also use a widget that lets you use PHP in the sidebar widgets... and put there your custom query. If you google it ("wp display posts from a category") you will, probably, find many answers.

Edit. P.S. Did you know you can also use 'tags' for grouping posts by certain criteria... just saying.

Yeah, you are right I was not using the wp terminology.

(i) I am talking of wordpress categories.

(ii) I will be using category widget to display the posts in the right side bar.

(iii) Instead of normal one wordpress category, I want to have two different wordpress categories, one "Manufactures of the Product" (say A, B & C, so on) and second "Price Range" of the products (under 100 $, 100-200$, 200-300$ and so on)

(iv) All the posts will come & appear in both the categories.

(v) Want to use widget to show both the categories in the side bar (as I don't know coding)

I hope, I am clear this time.