If your business is in the US, foreign suppliers are any manufacturers or distributors outside the country, while domestic ones are within the US like you. Generally, foreign suppliers can offer cheaper products, but they often take much longer to arrive (which is especially problematic if you're dropshipping, as customers don't want to wait weeks for their order). American brands often have a higher reputation for quality, and many customers will want to buy American anyway. However, if you do want to sell foreign brands, you can find a distributor within the US who has already imported the products for you, which cuts down significantly on the time it takes them to arrive (the long wait times only come into play when buying directly from a faraway manufacturer). You can also sell both foreign and domestic products together, unless part of your brand image involves only selling American products.