The difference between this and a firm is that a firm is the company that operates within the industry to create the product. The firm might be a factory, or the chain of stores that sells the clothes, within its industry. For example, one firm that makes steel might be Avida steel. They create the steel in that firm for the steel industry.
A firm is usually a corporate company that controls a number of chains in the industry it is operating within. For example in retail, the firm Arcadia stores owns the clothing chains Topshop, Dorothy Perkins, Miss Selfridge, and Evans. These all operate for the firm Arcadia within the industry of retail.
Several firms can operate in one industry to ensure that there is always competition to keep prices reasonable and stop the market becoming a monopoly, which is where one firm is in charge of the whole industry. Sometimes, a firm is not necessary within the industry and independent chains and retailers can enter straight into the market without a firm behind them, although this is risky. This is because one of the advantages of having a firm behind you is that it is a safeguard against possible bankruptcy because the firm can support the chain that it owns.