What is the difference between market share and sales volume?

Market share refers to the portion of total sales that a given company has, so if your company sells half of all the particular product that is sold by anybody, then you have a 50% market share. Sales volume is the actual amount, such as for example, $100,000 in sales. Or $100,000,000 as the case may be. Knowing the market share does not tell you the sales volume unless you also know what the total market volume is.