Variables are numbers that your typeform can keep track of. For example, you can keep a score, or calculate the price of an order. You can create as many different variables as you want, so you can track more than one score through your typeform, or whatever you decide.
If you want to display a Variable to your respondents, you can add it to your text using the @ symbol. This will bring up a list of all the information you can add to your text, including any Variables you have set up.
You can give each variable a base value, or leave it at 0 (zero), depending on what you want to do. If you had variables for different products in a shopping cart, you could specify the unit cost of each one here.
The Price variable is only available when you use a Payment question in your typeform.