Variable products are a super handy way to add products to your shop which have options without having to create the same product multiple times with small variations for each. A good example of this is you have sell shirts and the shirts come in a range of colours and you want the customer to be able to choose what colour shirt they want. The cool thing about variable products is that each variation can have its own product code, price, image and inventory quantity. Creating variable products can be a little tricky though so let's step through this process.
In the main menu go to Products and then All Products and select an existing product you want to edit or Add New to add a new product.
In the Product data box at the top you will see a dropdown, by default this will be set to Simple product, but you need to change this to Variable product.
Now we need to go to the Attributes tab and create the names of the variations. You will see a dropdown that says "Custom product attribute" and an Add button beside it, click on this button and a new attribute will be created.
We now need to give the attribute a name, so using the t shirt example we mention before we might call this "Colour", then in the Values box you need to enter in the names of the variations. This has to be done in a specific way, each variation needs to be separated by the pipe character "|" which is normally found above the enter/return key on your keyboard. So for the red and blue colours you would enter "red|blue" (without the quotes as shown below). Importantly, check the "Visible on the product page" and "Used for variations" checkboxes and then click the Save attributes button.
Now go to the Variations tab and in the dropdown select "Create variations from all attributes" and then click the Go button. Your variations will now be added below. Simply click on the variation and the box will expand with specific settings for the variation. This is where you can now enter specific information for the variation like its product code, price, stock quantity, weight, dimensions etc. You can do this for each variation.
Of course once you are done press the Save changes button at the bottom of the Product data box and update/publish the page.
Please view this video from 10 minutes and 16 seconds to view information about variable products.