Some very good information here - https://www.shopify.com/encyclopedia/business-license
Really depends where you are based.
Best of luck!
Aivis Zvezdovs / ANTI 404
Nick here from Shopify. Good question!
You wouldn't necessarily need a business license to sell on Shopify, but more from a legal business perspective. @Zvezdovs shared a great guide going into detail about business license definition, but I would also advise to check with your local tax office, accountant, or legal representative to see if you would need a license to sell sandwiches for tax and legal reasons more than anything.
You can also read more about licenses and permits from the USA Small Business administration website directly here.
Let me know if you have any other questions about this or setting up on Shopify!
All the best, Nick