What Does Android Market Mean?
The Android Market was an online store offering software applications designed for Android devices. Users gain access to the Android Market through its website or the Market application installed on Android mobile devices.
As of March 2012, Google rebranded/reorganized the Android Market into Google Play.
Techopedia Explains Android Market
Android apps are not only available on the Android Market. After registering for an Android Market account, developers may choose to make their apps available on their own websites. Developers pay a $25 one-time registration fee before they can start uploading applications to the Android Market. They need to open a Google Checkout Merchant account to receive payment. When a developer sells an app on the Android Market, Google gets 30 percent for each copy of the app downloaded.
The Android Market opened for business on October 22, 2008. While you won’t find it a "Android Market" now, the service does live on as Google Play.