It necessarily describes the kind of services offered and the price agreed for providing them. Usually, companies include their logo in the customer invoice template and, depending on the nature of business, they may mention the payment terms and the breakdown of goods or services offered.
Lastly, you will need to consider the production of your template. Depending on your industry you need to pick the best invoice to suit your needs. For example, you may use an invoice template that you customize electronically and print from the convenience of your office before submitting to your client.