It depends on the item — and we always show you at checkout. There are two models:
InHouse is the seller. You buy from us at your member price; we handle payment, tax, and returns, and the item is shipped from the brand on our behalf.
The brand is the seller. You buy directly from the brand — we connect you and may earn a commission, and that brand handles the sale, shipping, returns, and warranty.
In every case, the manufacturer makes the product and provides its warranty. The point is you'll never be in the dark — the seller is labeled before you pay.
This is why returns can differ by item — see "What's your return policy?"