Tags on stocks are for searching in Inventory a stock which contain that tag. For example, in Inventory you can add sorted stocks on a specific category (tags).

At the stocks that you're using in the kitchen, you can add the kitchen tag.

Also, tags could help you when you're searching for some specific stocks and you want to export them.

Adding tags on stocks it will be done from the Administrative part of your account. Go to the Stock Management app, then to Stocks tab.

After that, click on the 3 points button, from the right part.

Choose the Edit option.

It will show a new window, where you will enter the tag. After writing the tag, press enter, so that it will appear with a blue border. Don't forget to press Save.