To use tags in WordPress, watch this simple video tutorial which explains how to organise posts and incorporate searchable keywords.
Like categories, tags help to organize the posts on your site as well as provide searchable key-words that make it easier for users to find your content.
Tags are more descriptive than categories and are completely optional to your post.
To add a tag, simply go to the Tag box on the Edit Post screen.
You can type them in and hit Add or at hitting enter on your keyboard.
You can add multiple tags at a time by putting commas in between each word that you want to be a tag.
When you are done, hit Publish on your post.
Depending on your theme and widgets, your tags can be shown under posts or in the sidebar, which will lead to any other posts that you have used these tags in.