Market share is the percentage of sales (by value or volume) that a brand or company has for a specific product or category.
Note: Market share calculations can range from specific products (i.e. Vanilla flavored ready to drink iced coffee) to extremely broad industries (i.e. food and beverage). Be sure you are aware of which industry segment(s) a report includes.
Above is an image from IBIS World (an industry database) that shows the market share of the Car and Automobile Manufacturing Industry report.
Often, when looking up market information in search engines like Google, you will find all sorts of reports. However, you'll also find that most of the reports cost hundreds-thousands of dollars to access. We typically do not have access to these types of reports at Pitt, but it can be helpful to read the table of contents or preview they provide to help steer you in the right direction for additional information.