A sales associate, more than likely, works in a store or a fixed spot. You may get an hourly salary and a small commission.
Someone in sales, more than likely, contacts potential customers and tries to sell the product or services to them. You can be a sales rep in the garment industry, drug companies, construction, real estate, in fact, nearly any field.
Someone is sales relies mostly on commission. You may get a "draw against commission" meaning they will give you a salary to meet your needs, but your commissions will be deducted from that. Your commissions should far exceed your draw in a matter of weeks.
I worked in sales for years and liked being on commission because I was very good. If you are afraid of the word "no" or are not comfortable with being persistent, a sales associate job is for you. If you are willing to give it your all a job in sales can make you more money.
Be careful about the company you join. A friend of mine worked for Verizon. They promised him the world and he nearly went bankrupt waiting for their promises to come true.
Good luck! I hope I helped.