If you have your CRM settings configured to automatically generate quotes and invoices, accepted quotes will automatically convert to invoices.
The invoice will contain all of the same information as the quote, but it gives your customer the option to pay.
In order to disable quotes from automatically converting to invoices, you will want to disable your "create invoice" stage within your CRM settings and click save. Once a quote is accepted, it will stay as a quote and not convert to an invoice.