How to add and edit tags in WordPress
In WordPress you can assign one or more tags to each of your posts/articles. The tags are displayed on the frontend either under the content of the post or under its title (depending on the theme), and when a user clicks on a tag all the posts associated with the tag are listed.
To add and edit tags, log in to the admin panel and go to Posts menu>Tags submenu. If you have already added some tags, on the page that opens you'll see list with the most popular tags. On the left side of the page is the form for adding new tags and on the right side there is a table with the existing tags. The table consists of a few columns (Name, Description, Slug, Posts) displaying the relevant information for each tag. You can manage which columns are to be shown in the table and which are to be hidden. To do this click on the Screen Options button in the top right corner of the page and mark/unmark the respective checkboxes. Above and below the table there's a Bulk Actions drop-down menu with which you can delete many tags simultaneously. To do this, mark the checkboxes in the table corresponding to each of the tags that you want to delete, select Delete from the Bulk Actions drop-down menu and click on the Apply button.
Hovering the mouse pointer over a row in the table will display some buttons under the name of the particular tag. With the respective buttons you can delete the tag, you can view the tag page on the frontend; with the Quick Edit button you can edit the name and slug of the tag, while the Edit button will redirect you to the edit form. It's the same as the add form. There's a text field for the name of the tag and another one for the slug. The slug is the part of the URL address of the tag that corresponds to its name (e.g. hostknox-hosting in domain.com/?tag=hostknox-hosting). If you leave the Slug field empty, WordPress will create a slug automatically based on the name of the tag. There's also a text area for a description of the tag. If you want to, you can type some description. Whether it will be displayed on the frontend depends on the particular theme.
For some more details and screenshots check out the tutorial on how to manage tags in WordPress.