excuse me, but what is a market?

This just in:

IE lost market share in June, dipping to 86.56 percent from its May total of 87.23 percent, the report noted.

In 2005, Firefox increased its market hold every month between 0.5 percent and 1 percent, NetApplications.com said. The growth has come mainly at the expense of IE, which slips with every Firefox increase.

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I'm sorry, but isn't a market where a good or service is offered, and MONEY is paid in return? Correct me if I'm wrong, but aren't THESE BOTH FREE? HOW CAN A FREE PRODUCT LOSE MARKET SHARE?! THERE IS NO MARKET!