It's still on the rebound.Shopify (SHOP -1.05%) stock fell 15% in the first six months of the year, according to data provided by S&P Global Market Intelligence. It's still climbing back up from losses related to overexpanding its business and trading at a high valuation.Shopify is an e-commerce leaderShopify sells e-commerce services to business clients. It hosts a platform for small businesses to operate online, which is why you won't be buying products straight from Shopify. However, you're likely buying ...