Marketing and sales
Sales and marketing an essential part of your business: after all, you need customers. Marketing supports sales.
Speaking very generally: every business owner is a salesperson. This is all the more important when you are just starting out: you have to let people know about your business and what it offers. Marketing and sales help you achieve that.
Marketing helps potential customers find your business. With sales, you try to get them to buy.
Marketing and sales can be learned like anything else, so don’t stress if they are not immediately your strongest suit.